1.
How many molecules are there in one mole of H_{2}O?
Correct Answer
B. 6.023 x 10^{23}
Explanation
One mole of any substance contains Avogadro's number of particles, which is approximately 6.023 x 10^23. In the case of H2O, one mole of water contains 6.023 x 10^23 water molecules. Therefore, the correct answer is 6.023 x 10^23.
2.
A flask contains 500 cm^{3 }of SO_{2 }at STP. The flask contains?
Correct Answer
D. 1.427 g
Explanation
The given question states that a flask contains 500 cm3 of SO2 at STP. To determine the mass of the SO2 in the flask, we need to use the ideal gas law equation, PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature. At STP, the pressure is 1 atm and the temperature is 273 K. We can rearrange the equation to solve for n, the number of moles. The molar mass of SO2 is 64 g/mol. By substituting the given values into the equation, we can calculate that n is approximately 0.0223 mol. Finally, we can calculate the mass of SO2 by multiplying the number of moles by the molar mass, which gives us approximately 1.427 g.
3.
A necklace has 6 g of diamond in it. What are the number of atoms in it?
Correct Answer
D. 3.01 x 1023
Explanation
The answer, 3.01 x 10^23, is the correct option because it represents Avogadro's number, which is the number of atoms or molecules in one mole of a substance. In this case, since the necklace contains 6g of diamond, which has a molar mass of approximately 12g/mol, we can use the formula: number of atoms = (mass of substance / molar mass) x Avogadro's number. Plugging in the values, we get (6g / 12g/mol) x 6.02 x 10^23, which simplifies to 3.01 x 10^23 atoms.
4.
What is the mass of aluminum in 204 g of the aluminum oxide, Al_{2}O_{3}?
Correct Answer
D. 108 g
Explanation
The molar mass of Al2O3 is 102 g/mol. To find the mass of aluminum in 204 g of Al2O3, we need to calculate the mass of one mole of Al2O3 and then divide it by the molar mass of aluminum. Since there are 2 moles of aluminum in one mole of Al2O3, the mass of aluminum is 2 times the molar mass of aluminum. Therefore, the mass of aluminum in 204 g of Al2O3 is 2 * (26.98 g/mol) = 108 g.
5.
The reactant which is consumed earlier and gives least quantity of product is called
Correct Answer
C. Limiting reactant
Explanation
The limiting reactant is the reactant that is completely consumed in a chemical reaction, thereby limiting the amount of product that can be formed. It determines the maximum amount of product that can be obtained. In contrast, the reactant in excess is the reactant that is present in greater quantity than required for the reaction and is not completely consumed. The term "stoichiometry" refers to the quantitative relationship between reactants and products in a chemical reaction, while "stoichiometric amount" refers to the exact amount of reactants required for a reaction based on the stoichiometry.
6.
Which one of the following compounds contains the highest percentage by the mass of nitrogen
Correct Answer
B. N_{2}H_{4}
Explanation
N2H4 contains the highest percentage by mass of nitrogen because it has two nitrogen atoms in its formula, compared to only one nitrogen atom in the other compounds. Since the percentage by mass is calculated by dividing the mass of nitrogen in the compound by the total mass of the compound and multiplying by 100, having two nitrogen atoms in N2H4 increases the numerator and thus the percentage of nitrogen in the compound.
7.
Vitamin-A has a molecular formula C_{20}H_{30}O. The number of vitamin-A molecules in 500 mg of its capsule will be?
Correct Answer
B. 1.05 x 10^{21}
Explanation
The molecular formula of Vitamin-A is C20H30O, which means that it contains 20 carbon atoms, 30 hydrogen atoms, and 1 oxygen atom. To calculate the number of molecules in 500 mg of its capsule, we need to convert the mass of the capsule to moles using the molar mass of Vitamin-A. The molar mass of Vitamin-A can be calculated by adding the atomic masses of carbon, hydrogen, and oxygen. Once we have the number of moles, we can use Avogadro's number (6.02 x 10^23) to calculate the number of molecules. The correct answer, 1.05 x 10^21, is obtained by correctly performing these calculations.
8.
When one mole of each of the following is completely burnt in oxygen, which will give the largest mass of CO_{2}?
Correct Answer
C. Ethane
Explanation
When one mole of each substance is burnt in oxygen, the substance that will produce the largest mass of CO2 is ethane. This is because ethane (C2H6) has two carbon atoms, while the other substances have only one carbon atom. Since the number of carbon atoms directly affects the amount of CO2 produced, ethane will yield a larger mass of CO2 compared to the other substances.
9.
One mole of ethanol and one mole of ethane have an equal
Correct Answer
D. Number of molecules
Explanation
The correct answer is "Number of molecules." One mole of any substance contains Avogadro's number of particles, which is approximately 6.022 x 10^23. Therefore, both one mole of ethanol and one mole of ethane would have the same number of molecules, which is equal to Avogadro's number.
10.
Methane reacts with steam to form H_{2 }and CO as shown below.
What volume of H_{2 } can be obtained from 100 cm^{3 }of methane at the standard temperature and pressure?
Correct Answer
A. 300 cm^{3}
Explanation
When methane reacts with steam, it produces hydrogen gas (H2) and carbon monoxide (CO). The question asks for the volume of hydrogen gas that can be obtained from 100 cm3 of methane at standard temperature and pressure. Since the reaction is stoichiometric, it means that for every molecule of methane, one molecule of hydrogen gas is produced. Therefore, the volume of hydrogen gas obtained will be equal to the volume of methane used, which is 100 cm3.
11.
The Avogadro's constant is the number of?
Correct Answer
B. Molecules in 1 mole of a substance
Explanation
Avogadro's constant (6.022 × 10^23 mol-1) represents the number of particles, specifically molecules or atoms, in one mole of a substance. This constant allows chemists to relate the mass of a substance to the number of particles it contains. Option A is incorrect because it refers to the number of atoms in 12 grams of carbon-12, which is technically Avogadro's number (6.022 × 1023 atoms/mol), but it represents a specific isotope of carbon. Option C is incorrect because it refers to the number of electrons in 1 gram of hydrogen, which is unrelated to Avogadro's constant. Option D is incorrect because it mentions protons, whereas Avogadro's constant is associated with the number of molecules or atoms, not protons.
12.
How many mole of oxygen are needed for the complete combustion of two moles of butane?
Correct Answer
D. 13
Explanation
The complete combustion of butane (C4H10) requires 13 moles of oxygen. This can be determined by balancing the chemical equation for the combustion of butane, which is C4H10 + 13O2 -> 8CO2 + 10H2O. The equation shows that for every 1 mole of butane, 13 moles of oxygen are needed to produce 8 moles of carbon dioxide and 10 moles of water. Therefore, for 2 moles of butane, we would need 2 x 13 = 26 moles of oxygen.
13.
If four moles of SO_{2 }are oxidized to SO_{3 }, how many moles of oxygen molecules are required?
Correct Answer
D. 2.0
Explanation
When four moles of SO2 are oxidized to SO3, the balanced chemical equation shows that two moles of SO2 react with one mole of O2 to produce two moles of SO3. Therefore, to oxidize four moles of SO2, we would need two moles of O2.
14.
What is the mass of 2 moles of chlorine gas if the relative atomic mass of chlorine is 35.5 amu?
Correct Answer
B. 71 g
Explanation
The molar mass of chlorine gas (Cl2) is equal to the sum of the atomic masses of two chlorine atoms. Since the relative atomic mass of chlorine is 35.5 amu, the molar mass of chlorine gas is 2 * 35.5 = 71 g.
15.
Which of the following statements is incorrect?
Correct Answer
D. None of above
Explanation
The given question asks for the incorrect statement among the options. The correct answer is "None of above," which means that all of the statements are correct. This implies that 12 g of carbon gas does contain one mole of atoms, 28 g of nitrogen gas contains one mole of molecules of N2, and 1 dm3 of 1.0 mole dm-3 solution of NaCl does contain one mole of chloride ions.
16.
One mole of propane has the same
Correct Answer
A. Number of H- atoms as one mole of methane (CH_{4})
Explanation
One mole of propane (Câ‚ƒHâ‚ˆ) contains the same number of hydrogen atoms as one mole of methane (CHâ‚„). Both molecules have four hydrogen atoms. This equality arises from the stoichiometry of the compounds, where each carbon atom bonds with four hydrogen atoms in the respective molecules.
17.
What is the mass of one mole of iodine molecules?
Correct Answer
A. 254 g
Explanation
One mole of any substance is equal to its molar mass in grams. The molar mass of iodine (I2) is approximately 254 g/mol. Therefore, the mass of one mole of iodine molecules is 254 g.
18.
What volume of SO_{2 }at room temperature and pressure is produced on heating 9.7 g of Zinc sulphide (ZnS) if reaction takes place as follows?
Correct Answer
D. 2.38 liters