Chemistry B Quiz 4 Of 4

1. A sample of a compound is added to distilled water in a clean beaker. A reaction occurs, and the water temperature drops rapidly. Which of the following statements is best supported by this observation?

An endothermic reaction occurred.

A dehydration reaction occurred.

The water was originally warmer than the compound.

The beaker was contaminated by another compound.

The observation that the water temperature drops rapidly suggests that energy is being absorbed from the surroundings. This is characteristic of an endothermic reaction, where the reaction absorbs heat from its surroundings. Therefore, the best-supported statement is that an endothermic reaction occurred.

Explanation

The observation that the water temperature drops rapidly suggests that energy is being absorbed from the surroundings. This is characteristic of an endothermic reaction, where the reaction absorbs heat from its surroundings. Therefore, the best-supported statement is that an endothermic reaction occurred.

2.

178.3 kJ

571.8 kJ

−1029kJ

−2236kJ

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Explanation

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3. When zinc is exposed to air, zinc oxide is produced. What happens in this reaction?

Zinc is oxidized, and oxygen is reduced.

Zinc is reduced, and oxygen is oxidized.

Both zinc and oxygen are oxidized.

Both zinc and oxygen are reduced.

In this reaction, zinc is being oxidized, which means it is losing electrons. Oxygen, on the other hand, is being reduced, which means it is gaining electrons. This is evident from the formation of zinc oxide, where zinc atoms lose electrons to form positively charged zinc ions, and oxygen atoms gain these electrons to form negatively charged oxide ions. Therefore, the correct answer is that zinc is oxidized and oxygen is reduced.

Explanation

In this reaction, zinc is being oxidized, which means it is losing electrons. Oxygen, on the other hand, is being reduced, which means it is gaining electrons. This is evident from the formation of zinc oxide, where zinc atoms lose electrons to form positively charged zinc ions, and oxygen atoms gain these electrons to form negatively charged oxide ions. Therefore, the correct answer is that zinc is oxidized and oxygen is reduced.

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5.

A

B

C

D

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6.

They consist of barium chloride anhydrous.

They consist of barium chloride dihydrate.

They consist of barium chloride hexahydrate.

They consist of barium chloride heptahydrate.

The correct answer is "They consist of barium chloride dihydrate." This is because the term "dihydrate" indicates that the compound contains two molecules of water. The other options, such as anhydrous, hexahydrate, and heptahydrate, indicate different amounts of water molecules present in the compound, which are not consistent with the given statement.

Explanation

The correct answer is "They consist of barium chloride dihydrate." This is because the term "dihydrate" indicates that the compound contains two molecules of water. The other options, such as anhydrous, hexahydrate, and heptahydrate, indicate different amounts of water molecules present in the compound, which are not consistent with the given statement.

7.

544 mm Hg

784 mm Hg

1830 mm Hg

6212 mm Hg

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Explanation

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8. The equation below represents a chemical reaction that produces a gas. 2Na(s) + 2H O(l) → 2NaOH(aq) + H (g) 22 What is the theoretical yield in liters of H2 gas if 5.00 g of Na are completely reacted and the H2 gas is collected at STP?

0.109 L

2.44 L

4.88 L

5.09 L

The equation provided shows that 2 moles of Na react to produce 1 mole of H2 gas. To find the theoretical yield of H2 gas, we need to convert the given mass of Na to moles using its molar mass. Then, we can use the mole ratio from the balanced equation to calculate the moles of H2 gas produced. Finally, we can use the ideal gas law at STP (Standard Temperature and Pressure) to convert the moles of H2 gas to liters. The correct answer of 2.44 L is obtained by following these steps correctly.

Explanation

The equation provided shows that 2 moles of Na react to produce 1 mole of H2 gas. To find the theoretical yield of H2 gas, we need to convert the given mass of Na to moles using its molar mass. Then, we can use the mole ratio from the balanced equation to calculate the moles of H2 gas produced. Finally, we can use the ideal gas law at STP (Standard Temperature and Pressure) to convert the moles of H2 gas to liters. The correct answer of 2.44 L is obtained by following these steps correctly.

9. Which mixture can be separated through filtration because one of the substances is insoluble in water?

NaClO and Pb(ClO) 3

Na2SO4 and SrSO4

NaNO and Pb(NO)

NaCHO and Pb(CHO) 2

Na2SO4 and SrSO4 can be separated through filtration because one of the substances, SrSO4, is insoluble in water. Filtration is a method used to separate a solid from a liquid or gas by passing it through a filter, which allows the liquid or gas to pass through while retaining the solid. Since SrSO4 is insoluble in water, it will remain as a solid and can be separated from the liquid Na2SO4 through filtration.

Explanation

Na2SO4 and SrSO4 can be separated through filtration because one of the substances, SrSO4, is insoluble in water. Filtration is a method used to separate a solid from a liquid or gas by passing it through a filter, which allows the liquid or gas to pass through while retaining the solid. Since SrSO4 is insoluble in water, it will remain as a solid and can be separated from the liquid Na2SO4 through filtration.

10. What is the electron configuration for an atom of germanium at ground state?

[Ar]4s2 3d10 4p2

[Ar]4s2 4d10 4p2

[Kr]4s2 3d10 4p2

[Kr]4s2 4d10 4p2

The electron configuration for an atom of germanium at ground state is [Ar]4s2 3d10 4p2. This means that germanium has a total of 32 electrons. The [Ar] represents the electron configuration of the noble gas argon, which has 18 electrons. The 4s2 3d10 4p2 represents the remaining 14 electrons in the germanium atom, with 4s2 representing the 2 electrons in the 4th energy level (s sublevel), 3d10 representing the 10 electrons in the 3rd energy level (d sublevel), and 4p2 representing the 2 electrons in the 4th energy level (p sublevel).

Explanation

The electron configuration for an atom of germanium at ground state is [Ar]4s2 3d10 4p2. This means that germanium has a total of 32 electrons. The [Ar] represents the electron configuration of the noble gas argon, which has 18 electrons. The 4s2 3d10 4p2 represents the remaining 14 electrons in the germanium atom, with 4s2 representing the 2 electrons in the 4th energy level (s sublevel), 3d10 representing the 10 electrons in the 3rd energy level (d sublevel), and 4p2 representing the 2 electrons in the 4th energy level (p sublevel).

11.

F

G

H

J

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12. Heart cells require a certain balance of sodium and potassium ions to function. The blood, which is approximately 83% water, carries these two types of ions to the heart. The property of water that allows it to carry ions to the heart is its —

Molecular mass

Specific heat

Polarity

Density

Water is a polar molecule, meaning it has a slight positive charge on one end and a slight negative charge on the other end. This polarity allows water molecules to attract and surround ions, such as sodium and potassium ions, effectively carrying them in the bloodstream. The positive ends of water molecules attract negative ions, while the negative ends attract positive ions, creating a "hydration shell" around the ions and enabling their transport to the heart cells. Therefore, the property of water that allows it to carry ions to the heart is its polarity.

Explanation

Water is a polar molecule, meaning it has a slight positive charge on one end and a slight negative charge on the other end. This polarity allows water molecules to attract and surround ions, such as sodium and potassium ions, effectively carrying them in the bloodstream. The positive ends of water molecules attract negative ions, while the negative ends attract positive ions, creating a "hydration shell" around the ions and enabling their transport to the heart cells. Therefore, the property of water that allows it to carry ions to the heart is its polarity.

13. Use the equation below to answer the following question. BaCl (aq) + Na SO (aq) → 2NaCl(aq) + BaSO (s) 2244 The theoretical yield of BaSO4 is 58.35 g. If 44.34 g of BaSO4 are produced from the reaction shown above, what is the percent yield of BaSO4?

31.67%

52.03%

75.99%

85.17%

The percent yield can be calculated by dividing the actual yield (44.34 g) by the theoretical yield (58.35 g) and multiplying by 100. Therefore, the percent yield of BaSO4 is (44.34 g / 58.35 g) * 100 = 75.99%.

Explanation

The percent yield can be calculated by dividing the actual yield (44.34 g) by the theoretical yield (58.35 g) and multiplying by 100. Therefore, the percent yield of BaSO4 is (44.34 g / 58.35 g) * 100 = 75.99%.

14.

Volume

Mass

Boiling point

Number of moles

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Explanation

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15. What volume of 1.0 M sodium phosphate, to the nearest tenth of a liter, must be used to make 4.0 L of 0.80 M sodium phosphate? Record your answer and fill in the bubbles on your answer document.

To determine the volume of 1.0 M sodium phosphate needed, we can use the formula for dilution:

C1V1 = C2V2

Where C1 is the initial concentration (1.0 M), V1 is the initial volume (unknown), C2 is the final concentration (0.80 M), and V2 is the final volume (4.0 L).

Rearranging the formula, we have:

V1 = (C2V2) / C1

Plugging in the values, we get:

V1 = (0.80 M * 4.0 L) / 1.0 M = 3.2 L

Therefore, the volume of 1.0 M sodium phosphate needed is 3.2 liters.

Explanation

To determine the volume of 1.0 M sodium phosphate needed, we can use the formula for dilution:

C1V1 = C2V2

Where C1 is the initial concentration (1.0 M), V1 is the initial volume (unknown), C2 is the final concentration (0.80 M), and V2 is the final volume (4.0 L).

Rearranging the formula, we have:

V1 = (C2V2) / C1

Plugging in the values, we get:

V1 = (0.80 M * 4.0 L) / 1.0 M = 3.2 L

Therefore, the volume of 1.0 M sodium phosphate needed is 3.2 liters.

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16. As a distant star moves away from Earth, the light given off by the star has a measurably lower frequency. What happens to the wavelength and energy of the photons of light when the frequency becomes lower?

The wavelength becomes longer, and the energy decreases.

The wavelength becomes shorter, and the energy decreases.

The wavelength becomes longer, and the energy increases.

The wavelength becomes shorter, and the energy increases.

As the frequency of light decreases, the wavelength becomes longer. This is because frequency and wavelength are inversely proportional to each other. When the frequency decreases, the wavelength increases. Additionally, the energy of a photon is directly proportional to its frequency. So, when the frequency decreases, the energy of the photons also decreases. Therefore, the correct answer is that the wavelength becomes longer, and the energy decreases.

Explanation

As the frequency of light decreases, the wavelength becomes longer. This is because frequency and wavelength are inversely proportional to each other. When the frequency decreases, the wavelength increases. Additionally, the energy of a photon is directly proportional to its frequency. So, when the frequency decreases, the energy of the photons also decreases. Therefore, the correct answer is that the wavelength becomes longer, and the energy decreases.

17. Which of the following includes an example of a chemical property of an element?

Aluminum is a solid at room temperature and is a poor thermal insulator.

Sulfur is not shiny and is not malleable.

Sodium is a solid at room temperature and reacts with other elements.

Silicon is shiny and is a poor conductor of electricity.

The given answer is an example of a chemical property because it describes the reactivity of sodium with other elements. Chemical properties describe how a substance interacts with other substances and undergoes chemical changes. In this case, the fact that sodium reacts with other elements indicates a chemical property of sodium.

Explanation

The given answer is an example of a chemical property because it describes the reactivity of sodium with other elements. Chemical properties describe how a substance interacts with other substances and undergoes chemical changes. In this case, the fact that sodium reacts with other elements indicates a chemical property of sodium.

18. How many atoms are present in 179.0 g of iridium?

5.606×1023 atoms

6.464×1023 atoms

1.078 × 1026 atoms

1.157×1026 atoms

The correct answer is 5.606×10^23 atoms. This can be determined using the molar mass of iridium (192.22 g/mol) and Avogadro's number (6.022×10^23 atoms/mol). By dividing the given mass (179.0 g) by the molar mass, we can calculate the number of moles of iridium. Multiplying this by Avogadro's number gives us the number of atoms present in the given mass.

Explanation

The correct answer is 5.606×10^23 atoms. This can be determined using the molar mass of iridium (192.22 g/mol) and Avogadro's number (6.022×10^23 atoms/mol). By dividing the given mass (179.0 g) by the molar mass, we can calculate the number of moles of iridium. Multiplying this by Avogadro's number gives us the number of atoms present in the given mass.

19. How many molecules are in 0.500 mole of N2O5?

1.20×1023 molecules

3.01×1023 molecules

6.02×1023 molecules

3.01×1024 molecules

The Avogadro's number states that there are 6.02×10^23 molecules in one mole of any substance. Therefore, 0.500 mole of N2O5 would contain half of this number, which is 3.01×10^23 molecules.

Explanation

The Avogadro's number states that there are 6.02×10^23 molecules in one mole of any substance. Therefore, 0.500 mole of N2O5 would contain half of this number, which is 3.01×10^23 molecules.

20.

A Thermal energy → kinetic energy

B Kinetic energy → potential energy

C Chemical energy → thermal energy

D Potential energy → chemical energy

Chemical energy can be converted into thermal energy through a process called combustion. When a substance undergoes combustion, it releases energy in the form of heat. This heat energy is a form of thermal energy. Therefore, the conversion of chemical energy into thermal energy is a valid and well-known process.

Explanation

Chemical energy can be converted into thermal energy through a process called combustion. When a substance undergoes combustion, it releases energy in the form of heat. This heat energy is a form of thermal energy. Therefore, the conversion of chemical energy into thermal energy is a valid and well-known process.

21.

A heterogeneous mixture

An element

A compound

A homogeneous mixture

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Explanation

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22.

NaCl

KCl

KNO3

NaNO3

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Explanation

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23.

Trihydrogen phosphite

Phosphoric acid

Phosphorous hydroxide

Phosphorous acid

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Explanation

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24. Which of the following correctly matches a compound with its molecular geometry?

Water (H2O): linear

Carbon dioxide (CO ): tetrahedral 2

Ammonia (NH3): trigonal planar

Methane (CH4): tetrahedral

Methane (CH4) has a tetrahedral molecular geometry because it has four bonding pairs of electrons around the central carbon atom. In a tetrahedral arrangement, the four bonding pairs are arranged in a way that maximizes the distance between them, resulting in a symmetric shape with bond angles of approximately 109.5 degrees.

Explanation

Methane (CH4) has a tetrahedral molecular geometry because it has four bonding pairs of electrons around the central carbon atom. In a tetrahedral arrangement, the four bonding pairs are arranged in a way that maximizes the distance between them, resulting in a symmetric shape with bond angles of approximately 109.5 degrees.

25.

A

B

C

D

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26. Which of these is a postulate of kinetic molecular theory?

Molecules of gases have a finite volume.

Molecules of gases attract and repel one another.

Collisions between gas molecules are inelastic.

The kinetic energy of gas molecules depends on temperature.

According to the kinetic molecular theory, the kinetic energy of gas molecules depends on temperature. This means that as the temperature increases, the average kinetic energy of the gas molecules also increases. This postulate helps explain the relationship between temperature and the motion of gas molecules.

Explanation

According to the kinetic molecular theory, the kinetic energy of gas molecules depends on temperature. This means that as the temperature increases, the average kinetic energy of the gas molecules also increases. This postulate helps explain the relationship between temperature and the motion of gas molecules.

27. Which of these statements is an accurate description of the ionization energies of elements in the periodic table?

The ionization energy of lithium is greater than that of potassium.

The ionization energy of iodine is greater than that of fluorine.

The ionization energy of magnesium is greater than that of sulfur.

The ionization energy of krypton is greater than that of neon.

The ionization energy of an element refers to the amount of energy required to remove an electron from an atom of that element. In general, ionization energy tends to increase from left to right across a period in the periodic table, and decrease from top to bottom within a group. Therefore, the statement that the ionization energy of lithium is greater than that of potassium is accurate, as lithium is located to the left of potassium in the periodic table.

Explanation

The ionization energy of an element refers to the amount of energy required to remove an electron from an atom of that element. In general, ionization energy tends to increase from left to right across a period in the periodic table, and decrease from top to bottom within a group. Therefore, the statement that the ionization energy of lithium is greater than that of potassium is accurate, as lithium is located to the left of potassium in the periodic table.

28.

Nuclear fusion is occurring because many smaller nuclei are being fused.

Nuclear fission is occurring because large amounts of energy are being absorbed.

Nuclear fusion is occurring because many energetic neutrons are being emitted.

Nuclear fission is occurring because a nucleus is being split into smaller nuclei.

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Explanation

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29. Some students used a variety of procedures to investigate four liquid samples. The students recorded the following information. • When Sample W was cooled, solid particles settled out of the liquid. • The mass and volume of Sample X were measured, and the density of Sample X was calculated to be 1.6 g/mL. • Sample Y was heated, and the temperature was recorded. All the liquid boiled away at the same temperature and left no residue in the container. • When a dilute acid was added to Sample Z, gas bubbles formed and rapidly rose to the surface of the liquid. Based on these observations, which sample was clearly identifiable as a pure substance?

Sample W

Sample X

Sample Y

Sample Z

Sample Y is clearly identifiable as a pure substance because when it was heated, all the liquid boiled away at the same temperature and left no residue in the container. This indicates that Sample Y is a single, homogeneous substance without any impurities or contaminants.

Explanation

Sample Y is clearly identifiable as a pure substance because when it was heated, all the liquid boiled away at the same temperature and left no residue in the container. This indicates that Sample Y is a single, homogeneous substance without any impurities or contaminants.

30. In a famous experiment conducted by Ernest Rutherford, positively charged alpha particles were scattered by a thin gold foil. Which of the following is a conclusion that resulted from this experiment?

The nucleus is negatively charged.

The atom is a dense solid and is indivisible.

The mass is conserved when atoms react chemically.

The nucleus is very small and the atom is mostly empty space.

This conclusion was drawn from Rutherford's experiment because most of the alpha particles passed straight through the gold foil, indicating that they were passing through empty space in the atom. However, a small fraction of the alpha particles were deflected or bounced back, suggesting that they were encountering a small, dense, positively charged nucleus at the center of the atom. This led to the understanding that the nucleus is very small compared to the overall size of the atom and that the atom is mostly empty space.

Explanation

This conclusion was drawn from Rutherford's experiment because most of the alpha particles passed straight through the gold foil, indicating that they were passing through empty space in the atom. However, a small fraction of the alpha particles were deflected or bounced back, suggesting that they were encountering a small, dense, positively charged nucleus at the center of the atom. This led to the understanding that the nucleus is very small compared to the overall size of the atom and that the atom is mostly empty space.

31.

Liquid condenses on a cold glass rod when gas from the test tube on the left is released.

A gas probe indicates that the water in the beaker contains dissolved nitrogen and oxygen.

A burning wood splint placed above the mouth of the test tube on the right glows brighter when some gas is released from the test tube.

The temperature of the wire connected to the battery increases.

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32.

It is a pure substance because solid particles cannot pass through the filter paper.

It is a pure substance because the river water is composed only of free elements.

It is a mixture because dissolved ions in the water pass through the filter paper.

It is a mixture because solid particles are separated from the river water.

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Explanation

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33.

Indium (In), because it has a slightly higher atomic mass than aluminum (Al), and tin (Sn), because it has a slightly higher atomic mass than silicon (Si)

Cadmium (Cd), because it has chemical properties similar to those of zinc (Zn), and mercury (Hg), because it has chemical properties similar to those of arsenic (As)

Antimony (Sb), because it has a slightly higher atomic mass than zinc (Zn), and bismuth (Bi), because it also has a higher atomic mass than zinc (Zn)

Gallium (Ga), because it has chemical properties similar to those of aluminum (Al), and germanium (Ge), because it has chemical properties similar to those of silicon (Si)

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Explanation

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34. Which product balances the chemical equation below? 3AgNO3(aq) + FeCl3(aq) → 3AgCl(s) + ______________

FeCl(aq)

FeCl2(aq)

FeNO3(aq)

Fe(NO3)3(aq)

The balanced chemical equation shows that 3 moles of AgNO3 react with 1 mole of FeCl3 to produce 3 moles of AgCl. The missing product must be able to provide 3 moles of Cl ions to react with the AgNO3. Among the given options, only Fe(NO3)3(aq) contains 3 moles of NO3 ions, which can provide the required Cl ions when combined with FeCl3. Therefore, Fe(NO3)3(aq) is the correct answer.

Explanation

The balanced chemical equation shows that 3 moles of AgNO3 react with 1 mole of FeCl3 to produce 3 moles of AgCl. The missing product must be able to provide 3 moles of Cl ions to react with the AgNO3. Among the given options, only Fe(NO3)3(aq) contains 3 moles of NO3 ions, which can provide the required Cl ions when combined with FeCl3. Therefore, Fe(NO3)3(aq) is the correct answer.

35. Chemists can identify the composition of some unknown salts by conducting a flame test. When potassium salts are heated in a flame, a purple color is observed. This is due to the movement of electrons between energy levels. What is the electron configuration of a potassium atom at ground state?

1s22s22p63s23p64d1

1s22s22p63s23p63d1

1s22s22d63s23d64s1

1s22s22p63s23p64s1

The electron configuration of a potassium atom at ground state is 1s22s22p63s23p64s1. This means that there are two electrons in the 1s orbital, two electrons in the 2s orbital, six electrons in the 2p orbital, two electrons in the 3s orbital, six electrons in the 3p orbital, and one electron in the 4s orbital. This configuration allows for the movement of electrons between energy levels, which is responsible for the observed purple color during a flame test.

Explanation

The electron configuration of a potassium atom at ground state is 1s22s22p63s23p64s1. This means that there are two electrons in the 1s orbital, two electrons in the 2s orbital, six electrons in the 2p orbital, two electrons in the 3s orbital, six electrons in the 3p orbital, and one electron in the 4s orbital. This configuration allows for the movement of electrons between energy levels, which is responsible for the observed purple color during a flame test.