The Officials Chm101 CBT Practice
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Molarity is defined as ______
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Moles of solute per liter of solution
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Moles of solute per litre of solvent
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Moles of solvent per liter of solution
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Moles solvent per liter of solvent
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Quiz Preview
- 2.
The Element that best describes Alpha decay is?
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Helium
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Sodium
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Calcium
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Methane
Correct Answer
A. HeliumExplanation
Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle, which consists of two protons and two neutrons. The only option that corresponds to an alpha particle is Helium, as it has two protons and two neutrons in its nucleus. Sodium, Calcium, and Methane do not have the same composition as an alpha particle, so they do not best describe alpha decay.Rate this question:
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- 3.
What is the name of the CEO of The Officials Educational consult?
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Femi Ajewole
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Williams David
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King Adewole David
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Oyewole Kolawole David
Correct Answer
A. Oyewole Kolawole David -
- 4.
What is the Mass number of Na?
Correct Answer
23Explanation
The mass number of an element represents the total number of protons and neutrons in its nucleus. Sodium (Na) has an atomic number of 11, which means it has 11 protons. To find the mass number, we can look at the periodic table and see that the atomic mass of sodium is approximately 23. This means that sodium has 12 neutrons (23 - 11 = 12). Therefore, the mass number of Na is 23.Rate this question:
- 5.
What is the oxidation number of the chromium atom in K2Cr2O7
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-2
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+3
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+6
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+7
Correct Answer
A. +6Explanation
In potassium dichromate K2Cr2O7 the oxidation number of potassium (K) is +1, and the oxidation number of oxygen (O) is typically -2. Since the compound is neutral, the sum of the oxidation numbers must be zero. Therefore, the oxidation number of chromium (Cr) is calculated to be +6.Rate this question:
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- 6.
How many grams of KNO3 are needed to make 250ML of a solution that is 0.135M
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1.71g
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0.341g
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3.41g
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6.82g
Correct Answer
A. 3.41gExplanation
To calculate the grams of KNO3 needed, we can use the formula: Molarity (M) = moles of solute / volume of solution (L). Rearranging the formula, we can calculate the moles of KNO3 needed by multiplying the molarity by the volume in liters. In this case, the molarity is 0.135M and the volume is 250 mL, which is 0.25L. Multiplying these values gives us 0.03375 moles of KNO3. To convert moles to grams, we multiply by the molar mass of KNO3, which is 101.1 g/mol. Multiplying 0.03375 moles by 101.1 g/mol gives us 3.41g of KNO3 needed.Rate this question:
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- 7.
Of the following, which element has the highest first ionization energy
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Iodine
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Bromine
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Fluorine
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Chlorine
Correct Answer
A. FluorineExplanation
Fluorine has the highest first ionization energy among the given elements. Ionization energy is the energy required to remove an electron from an atom. Fluorine, being the smallest element in the group, has the highest effective nuclear charge, meaning its nucleus exerts a stronger pull on its electrons. This makes it more difficult to remove an electron from a fluorine atom, resulting in a higher ionization energy compared to iodine, bromine, and chlorine.Rate this question:
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- 8.
Isotopes have the same number of __________ but different numbers of ___________ in their nuclei
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Electron, neutron
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Protons, neutrons
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Protons, electrons
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Nucleon, neutron
Correct Answer
A. Protons, neutronsExplanation
Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons in their nuclei. The number of protons determines the element's identity, while the number of neutrons affects the atom's mass. Therefore, isotopes of the same element have the same number of protons (which gives them the same atomic number) but different numbers of neutrons (which gives them different atomic masses).Rate this question:
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- 9.
Which of the following is not an Arrhenius acid?
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HF
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KOH
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HCLO
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H2SO3
Correct Answer
A. KOHExplanation
KOH is not an Arrhenius acid because it does not produce H+ ions when dissolved in water. Instead, it produces OH- ions, making it a strong base. Arrhenius acids are substances that release H+ ions in water, such as HF, HCLO, and H2SO3.Rate this question:
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- 10.
Which of the following can be classified as a weak base?
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CH3NH2
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NH2OH
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Both CH3NH2 and NH2OH
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Neither A nor B
Correct Answer
A. Both CH3NH2 and NH2OHExplanation
Both CH3NH2 and NH2OH can be classified as weak bases because they are both organic compounds that can accept protons (H+) but only to a limited extent. Weak bases, unlike strong bases, do not completely dissociate in water and do not fully accept protons. CH3NH2 is methylamine, which is a weak base due to the presence of the amino group (NH2). NH2OH is hydroxylamine, which is also a weak base because of the presence of the hydroxyl group (OH). Therefore, both CH3NH2 and NH2OH can be classified as weak bases.Rate this question:
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- 11.
Which of the following can be interpreted as a measure of randomness
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Enthalpy
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Entropy
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Free Energy
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Temperature
Correct Answer
A. EntropyExplanation
Entropy can be interpreted as a measure of randomness because it quantifies the degree of disorder or randomness in a system. It is a fundamental concept in thermodynamics and statistical mechanics, and it describes the number of possible microstates that a system can occupy at a given macrostate. A higher entropy value indicates a greater degree of randomness, while a lower entropy value indicates a more ordered or structured system. Therefore, entropy is a suitable measure for quantifying randomness in a system.Rate this question:
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- 12.
The energy of motion is
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Electrical Energy
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Dam energy
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Reserve energy
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Kinetic Energy
Correct Answer
A. Kinetic EnergyExplanation
Kinetic energy is the energy possessed by an object due to its motion. It is directly proportional to the mass and the square of the velocity of the object. The faster an object moves or the more mass it has, the greater its kinetic energy. In this context, electrical energy, dam energy, and reserve energy do not specifically refer to the energy of motion. Therefore, the correct answer is kinetic energy.Rate this question:
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- 13.
What is the minimum energy barrier that must be overcome for a chemical reaction to occur
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Activation Energy
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Net energy
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Potential energy
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Rate limiting energy
Correct Answer
A. Activation EnergyExplanation
Activation Energy is the minimum energy barrier that must be overcome for a chemical reaction to occur. It represents the energy required to break the bonds of the reactants and initiate the reaction. Without reaching this energy threshold, the reaction will not proceed. Activation Energy is a fundamental concept in chemistry and is essential for understanding reaction rates and the factors that influence them.Rate this question:
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- 14.
What is the overall reaction order for the reaction that has the rate law: k[H2] [NO] 2
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Zero order
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First order
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Second order
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Third order
Correct Answer
A. Third orderExplanation
The overall reaction order for a reaction is determined by summing the individual orders of all the reactants in the rate law. In this case, the rate law is given as k[H2][NO]^2. The order of [H2] is 1, the order of [NO] is 2, therefore the overall reaction order is 1 + 2 = 3, making it a third order reaction.Rate this question:
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- 15.
A catalyst increases the rate of reaction by providing a different reaction pathway that
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Lowers only the activation Energy
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Raises only the energy of the products
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Lowers only the energy of the reactants and products
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All of these are affected by the presence of a catalyst
Correct Answer
A. Lowers only the activation EnergyExplanation
A catalyst increases the rate of reaction by lowering only the activation energy. Activation energy is the minimum energy required for a reaction to occur. By providing an alternative reaction pathway with a lower activation energy, a catalyst allows more reactant molecules to have enough energy to overcome the activation energy barrier and participate in the reaction. This lowers the energy barrier for the reaction and increases the reaction rate. The energy of the products and reactants is not affected by the presence of a catalyst, only the activation energy is lowered.Rate this question:
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- 16.
The number of nucleons in an atom or ion is the same as the
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Atomic Number
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Charge on the atom or ion
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Mass Number
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None of these
Correct Answer
A. Mass NumberExplanation
The mass number of an atom or ion represents the total number of protons and neutrons in its nucleus. Since nucleons include both protons and neutrons, the number of nucleons in an atom or ion is the same as its mass number. The atomic number represents the number of protons in the nucleus, and the charge on the atom or ion refers to the number of electrons gained or lost. Therefore, neither the atomic number nor the charge on the atom or ion is the same as the number of nucleons.Rate this question:
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- 17.
The binding energy is defined as
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The amount of energy absorbed when electrons are added to an ion.
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The amount of energy absorbed when protons and neutrons form a nucleus
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The amount of energy released when electrons are removed from the atom
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The amount of energy required to break apart a nucleus into individual protons and neutrons
Correct Answer
A. The amount of energy required to break apart a nucleus into individual protons and neutronsExplanation
The binding energy refers to the amount of energy that is required to break apart a nucleus into individual protons and neutrons. This energy is necessary to overcome the forces that hold the nucleus together. By breaking apart the nucleus, the protons and neutrons are separated, and this requires an input of energy. Therefore, the correct answer is that the binding energy is the amount of energy required to break apart a nucleus into individual protons and neutrons.Rate this question:
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- 18.
Elements with ___________ atomic mass are best possible candidates for a fusion reaction
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Very low
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Moderate
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Moderate to heavy
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Very heavy
Correct Answer
A. Very lowExplanation
Elements with very low atomic mass are best possible candidates for a fusion reaction because fusion reactions involve the combining of two lighter atomic nuclei to form a heavier nucleus. The energy released during this process is related to the difference in mass between the reactants and the product. Therefore, elements with very low atomic mass have a greater potential for fusion reactions as they can release a significant amount of energy.Rate this question:
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- 19.
Radiation is detected by its ___________ properties
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Gravitational
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Ionizing
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Kinetic
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Thermal
Correct Answer
A. IonizingExplanation
Radiation is detected by its ionizing properties. Ionizing radiation refers to radiation that has enough energy to remove tightly bound electrons from atoms, creating charged particles called ions. This type of radiation can cause damage to living tissues and is commonly used in medical imaging and cancer treatment. By detecting the ionizing properties of radiation, scientists and medical professionals can measure and monitor its presence, intensity, and potential harmful effects.Rate this question:
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- 20.
What is the field of the CEO of The Officials Educational consult?
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Mass Communication
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Computer Engineering
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Mechatronics Engineering
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Pure Chemistry
Correct Answer
A. Mechatronics EngineeringExplanation
The correct answer is Mechatronics Engineering. This is the field of the CEO of The Officials Educational consult.Rate this question:
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- 21.
The effect of ionizing radiation depend on
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Length of exposure to radiation
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Location of source (internal or external)
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Type and energy of radiation
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All of the above
Correct Answer
A. All of the aboveExplanation
The effect of ionizing radiation depends on multiple factors, including the length of exposure to radiation, the location of the radiation source (whether it is internal or external to the body), and the type and energy of the radiation. All of these factors play a role in determining the potential harm caused by ionizing radiation.Rate this question:
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- 22.
Who is the Dean of Faculty of Science in Fuoye
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Dr. Lawal
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Dr. Malomo
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Dr. Okolo
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Dr. Shakirudeen
Correct Answer
A. Dr. Lawal -
- 23.
What is the mole fraction of ethanol in a solution made by dissolving 25g of ethanol, C2H5OH, in 53.6g of Water?
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0.154
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0.846
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0.214
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0.272
Correct Answer
A. 0.154Explanation
The mole fraction of a component in a solution is defined as the ratio of the number of moles of that component to the total number of moles of all components in the solution. In this case, we need to calculate the moles of ethanol and water separately.
To calculate the moles of ethanol, we divide the given mass of ethanol (25g) by its molar mass (46.07 g/mol). This gives us approximately 0.543 moles of ethanol.
To calculate the moles of water, we divide the given mass of water (53.6g) by its molar mass (18.015 g/mol). This gives us approximately 2.97 moles of water.
The total number of moles in the solution is the sum of the moles of ethanol and water, which is approximately 3.513 moles.
To find the mole fraction of ethanol, we divide the moles of ethanol by the total number of moles in the solution. This gives us approximately 0.154, which is the correct answer.Rate this question:
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- 24.
What is the expected freezing point of a 0.50m solution of Na2CO3 in water? Kf for water is 1.86°C/m
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-0.93°C
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-1.9°C
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-2.8°C
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-6.5°C
Correct Answer
A. -2.8°CExplanation
The expected freezing point of a solution can be calculated using the formula: ΔT = Kf * m, where ΔT is the change in freezing point, Kf is the cryoscopic constant, and m is the molality of the solution. In this case, the molality is given as 0.50m and Kf for water is given as 1.86°C/m. Plugging in the values, we get ΔT = 1.86 * 0.50 = 0.93°C. Since the freezing point is expected to decrease, the answer would be -0.93°C. However, the given options are in degrees Celsius, so the answer should be -0.93°C converted to -2.8°C.Rate this question:
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- 25.
Which cell involves a non-spontaneous redox reaction?
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Concentration cell
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Electrolytic Cell
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Fuel Cell
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Galvanic cell
Correct Answer
A. Electrolytic CellExplanation
An electrolytic cell involves a non-spontaneous redox reaction. Unlike galvanic cells, which produce electrical energy from spontaneous redox reactions, electrolytic cells use electrical energy to drive a non-spontaneous redox reaction. In an electrolytic cell, an external power source is used to force electrons to flow in the opposite direction, causing a non-spontaneous reduction and oxidation to occur. This process is commonly used in processes such as electroplating and electrolysis.Rate this question:
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- 26.
During an electrochemical reaction, electrons move through the external circuit toward the __________ and positive ion in the cell move toward the ____________.
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Anode, anode
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Anode, cathode
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Cathode, anode
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Cathode, cathode
Correct Answer
A. Cathode, cathodeExplanation
During an electrochemical reaction, electrons move through the external circuit toward the cathode and positive ions in the cell move toward the cathode. This is because the cathode is the electrode where reduction occurs, meaning it gains electrons. On the other hand, the anode is the electrode where oxidation occurs, meaning it loses electrons. Therefore, the movement of electrons is from the anode to the cathode, while the movement of positive ions is also toward the cathode.Rate this question:
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- 27.
How many grams of chromium metal are plated out when a constant current of 8.00A is passed through an aqueous solution containing Cr3+ ions for 40 minutes
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3.45g
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6.15g
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10.3g
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31.0g
Correct Answer
A. 3.45gExplanation
To calculate the amount of chromium metal plated out, we can use Faraday's law of electrolysis. According to this law, the mass of a substance deposited on an electrode is directly proportional to the amount of charge passed through the electrolyte. The formula to calculate the mass is:
Mass = (Current × Time × Atomic mass) / (Number of electrons × Faraday's constant)
In this case, the current is 8.00A, the time is 40 minutes (which needs to be converted to seconds), the atomic mass of chromium is 52 g/mol, the number of electrons involved in the reaction is 3, and the Faraday's constant is 96,485 C/mol.
Converting the time to seconds: 40 minutes × 60 seconds/minute = 2400 seconds
Using the formula:
Mass = (8.00A × 2400s × 52g/mol) / (3 × 96,485 C/mol)
Calculating the mass gives us approximately 3.45g. Therefore, the correct answer is 3.45g.Rate this question:
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- 28.
How many grams of nickel metal are plated out when a constant current of 15.0A is passed through aqueous NiCl2 for 80.0 minutes
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14.7g
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21.9g
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43.8g
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48.4g
Correct Answer
A. 21.9gExplanation
To calculate the amount of nickel metal plated out, we need to use Faraday's law of electrolysis. The formula is:
mass (in grams) = (current (in amperes) x time (in seconds) x molar mass of the metal) / (number of electrons transferred x Faraday's constant)
Given that the current is 15.0A, the time is 80.0 minutes (which is equal to 4800 seconds), and the molar mass of nickel is 58.69 g/mol, we can calculate the mass of nickel plated out using the formula above. Plugging in the values, we get:
mass = (15.0A x 4800s x 58.69g/mol) / (2 x 96485 C/mol)
Simplifying the equation gives us a mass of approximately 21.9g. Therefore, the correct answer is 21.9g.Rate this question:
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- 29.
Which of the following supports Boyles law
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K=PV
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NRT=KV
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PV/R
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T = KV
Correct Answer
A. K=PVExplanation
The equation K=PV represents Boyle's law, which states that the pressure of a gas is inversely proportional to its volume at a constant temperature. In this equation, K represents the constant factor, P represents the pressure of the gas, and V represents its volume. As the volume of a gas increases, the pressure decreases, and vice versa, as long as the temperature remains constant. Therefore, the equation K=PV supports Boyle's law.Rate this question:
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- 30.
What is the identity of the element with 6 protons, 7 neutrons and 6 electrons?
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C
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N
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Al
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Mg
Correct Answer
A. CExplanation
The element with 6 protons, 7 neutrons, and 6 electrons is carbon (C). The number of protons determines the atomic number, which is unique to each element. Carbon has an atomic number of 6, meaning it has 6 protons. The number of neutrons can vary within an element, resulting in different isotopes, but the atomic number remains the same. Therefore, the given combination of protons, neutrons, and electrons corresponds to carbon.Rate this question:
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- 31.
Chlorine belongs to the ____________ group on the periodic table
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Alkali metal
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Alkaline earth metal
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Halogen
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Noble
Correct Answer
A. HalogenExplanation
Chlorine belongs to the halogen group on the periodic table because it is a highly reactive nonmetal. Halogens are located in Group 17 of the periodic table and include elements such as fluorine, chlorine, bromine, iodine, and astatine. These elements have seven valence electrons and readily form compounds by gaining one electron to achieve a stable electron configuration. Chlorine, specifically, is known for its strong disinfectant properties and is commonly used in water treatment and as a bleach.Rate this question:
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- 32.
Water is an example of
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Compound
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An element
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A mixture
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An ion
Correct Answer
A. CompoundExplanation
Water is an example of a compound because it is made up of two different elements, hydrogen and oxygen, that are chemically bonded together. In a compound, the elements lose their individual properties and form a new substance with its own unique properties. Water has distinct physical and chemical properties that are different from those of hydrogen and oxygen. Therefore, it is considered a compound rather than an element, mixture, or ion.Rate this question:
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- 33.
Elements in a periodic group have similar
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Chemical properties
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Densities
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Masses
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Physical properties
Correct Answer
A. Chemical propertiesExplanation
Elements in a periodic group have similar chemical properties because they have the same number of valence electrons, which determines their reactivity and the types of chemical bonds they can form. This similarity in chemical properties allows elements in the same group to exhibit similar behavior in chemical reactions and to form similar compounds.Rate this question:
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- 34.
The factor 0.001 corresponds to which prefix
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Deka
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Deci
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Centi
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Milli
Correct Answer
A. MilliExplanation
The factor 0.001 corresponds to the prefix "Milli". This prefix is used to indicate one thousandth of a unit. For example, one millimeter is equal to one thousandth of a meter. Therefore, the correct answer is "Milli".Rate this question:
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- 35.
Which group reacts violently with water?
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Halogens
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Noble gases
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Alkali metals
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Alkaline earth metal
Correct Answer
A. Alkali metalsExplanation
Alkali metals react violently with water because they have a single valence electron, which they readily lose in order to achieve a stable electron configuration. When alkali metals come into contact with water, they undergo a vigorous reaction, producing hydrogen gas and forming hydroxide ions. This reaction is highly exothermic and can even result in explosions or fires, making alkali metals highly reactive and dangerous when exposed to water.Rate this question:
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