Mole & Mass MCQ's PDF

1. What is the number of moles in 22g of CO\(_2\) (molar mass of CO\(_2\) is 44 g/mol)? a) 0.5 b) 1 c) 2 d) 3 Answer: a) 0.5 Explanation: Number of moles = 22 / 44 = 0.5. 2. Find the mass of 2 moles of H\(_2\)O (molar mass of H\(_2\)O is 18 g/mol). a) 36g b) 9g c) 27g d) 45g Answer: a) 36g Explanation: Mass \( = \text{number of moles} \times \text{molar mass} = 2 \times 18 = 36 \)g. 3. How many moles are in 85g of Na (molar mass of Na is 23 g/mol)? a) 2.13 b) 3.70 c) 4.45 d) 5.17 Answer: d) 3.70 Explanation: Number of moles \( = \frac{\text{mass}}{\text{molar mass}} = \frac{85}{23} \approx 3.70 \). 4. Determine the mass of 0.25 moles of Mg (molar mass of Mg is 24 g/mol). a) 6g b) 12g c) 24g d) 48g Answer: a) 6g Explanation: Mass \( = \text{number of moles} \times \text{molar mass} = 0.25 \times 24 = 6 \)g. 5. Calculate the number of moles in 125g of Fe (molar mass of Fe is 56 g/mol). a) 1.75 b) 2.2 c) 2.4 d) 2.5 Answer: a) 2.23 Explanation: Number of moles \( = \frac{\text{mass}}{\text{molar mass}} = \frac{125}{56} \approx 2.23 \). 6. How many grams are in 3 moles of Al\(_2\)O\(_3\) (molar mass of Al\(_2\)O\(_3\) is 102 g/mol)? a) 204g b) 306g c) 102g d) 510g Answer: b) 306g Explanation: Mass \( = \text{number of moles} \times \text{molar mass} = 3 \times 102 = 306\)g. 7. What is the de nition of relative atomic mass (Ar)? a) Mass of one atom of an isotope relative to 1/12th the mass of a \(^{12}C\) atom b) Weighted average mass of one atom of an element relative to the mass of a \(^{12}C\) atom c) Mass of one ion relative to a \(^{12}C\) atom d) Average mass of one molecule Answer: b) Weighted average mass of one atom of an element relative to the mass of a \(^{12} C\) atom Explanation: It takes into account all isotopes of the element and their abundance. 8. What is the de nition of Avogadro’s constant? a) Number of molecules in one mole of a substance b) Number of atoms in one mole of any substance c) Number of particles in one mole of a substance d) Number of ions in one mole of any element Answer: c) Number of particles in one mole of a substance Explanation: Avogadro’s constant is \(6.02 \times 10^{23}\) particles per mole. 9. What is the de nition of molar mass? a) The mass in grams of one mole of a substance b) The mass of one atom of a substance c) The mass in kilograms of one mole of a substance d) The mass of 12 grams of carbon-12 Answer: a) The mass in grams of one mole of a substance Explanation: The molar mass is the mass of one mole of atoms, molecules, or ions in grams. 10. What does the relative molecular mass (Mr) of a compound represent? a) The mass of one molecule relative to an atom of hydrogen b) The average mass of one molecule relative to one atom of \(^{12}C\) c) The mass of one mole of molecules in kilograms d) The number of particles per mole of the compound Answer: b) The average mass of one molecule relative to one atom of \(^{12}C\) Explanation: The relative molecular mass is determined by the sum of the atomic masses of the elements in the compound relative to \(^{12}C\). #### Calculations Involving Avogadro’s Constant: 11. How many molecules are in 0.5 moles of H\(_2\)O? \((\text{Avogadro's constant} = 6.02 \times 10^{23})\) a) \(3.01 \times 10^{23}\) b) \(1.204 \times 10^{24}\) c) \(6.02 \times 10^{23}\) d) \(2.05 \times 10^{23}\) Answer: a) \(3.01 \times 10^{23}\) Explanation: Number of molecules \( = \text{number of moles} \times \text{Avogadro's constant} = 0.5 \times 6.02 \times 10^{23} = 3.01 \times 10^{23} \). 12. Find the number of atoms in 2 moles of helium (He). a) \(1.204 \times 10^{24}\) b) \(2.05 \times 10^{23}\) c) \(1.508 \times 10^{24}\) d) \(6.02 \times 10^{23}\) Answer: a) \(1.204 \times 10^{24}\) Explanation: Number of atoms \( = 2 \times 6.02 \times 10^{23} = 1.204 \times 10^{24} \). fi fi fi 13. How many moles of Fe are there with \(1.204 \times 10^{24}\) atoms? a) 1 b) 2 c) 3 d) 4 Answer: b) 2 Explanation: Number of moles \( = \frac{\text{number of particles}}{\text{Avogadro's constant}} = \frac{1.204 \times 10^{24}}{6.02 \times 10^{23}} = 2 \). 14. Calculate the number of Cl\(_2\) molecules in 3 moles of chlorine gas. a) \(2.01 \times 10^{24}\) b) \(9.03 \times 10^{23}\) c) \(1.81 \times 10^{24}\) d) \(1.204 \times 10^{24}\) Answer: a) \(1.806 \times 10^{24}\) Explanation: Number of molecules \( = 3 \times 6.02 \times 10^{23} = 1.806 \times 10^{24} \). 15. How many moles are in \(3.61 \times 10^{24}\) molecules of \( NH_3\)? a) 4 b) 3 c) 5 d) 6 Answer: c) 6 Explanation: Number of moles = \(\frac{\text{Number of molecules}}{\text{Avogadro's constant}} = \frac{3.61 \times 10^{24}}{6.02 \times 10^{23}} = 6 \). 16. What is the density of a substance if its mass is 200g and its volume is 50cm\(^3\)? a) 6 g/cm\(^3\) b) 4 g/cm\(^3\) c) 5 g/cm\(^3\) d) 3 g/cm\(^3\) Answer: c) 4 g/cm\(^3\) Explanation: Density \( = \frac{\text{mass}}{\text{volume}} = \frac{200}{50} = 4 \)g/cm\(^3\). 17. Find the mass of a block with a density of 2.5 g/cm\(^3\) and a volume of 40 cm\(^3\). a) 30g b) 40g c) 80g d) 100g Answer: d) 100g Explanation: Mass = Density \(\times\) Volume = \(2.5 \times 40 = 100\)g. 18. How do you calculate the volume if the mass is 60g and the density is 3 g/cm\(^3\)? a) 20 cm\(^3\) b) 30 cm\(^3\) c) 40 cm\(^3\) d) 50 cm\(^3\) Answer: a) 20 cm\(^3\) Explanation: Volume \(= \frac{\text{mass}}{\text{density}} = \frac{60}{3} = 20 \)cm\(^3\). 19. Calculate the density if the mass is 150g and the volume is 25 cm\(^3\). a) 6 g/cm\(^3\) b) 4 g/cm\(^3\) c) 5 g/cm\(^3\) d) 7 g/cm\(^3\) Answer: c) 6 g/cm\(^3\) Explanation: Density \( = \frac{\text{mass}}{\text{volume}} = \frac{150}{25} = 6 \)g/cm\(^3\). 20. Find the volume of a liquid with a mass of 85g and a density of 1.7 g/cm\(^3\). a) 10 cm\(^3\) b) 20 cm\(^3\) c) 30 cm\(^3\) d) 50 cm\(^3\) Answer: b) 50 cm\(^3\) Explanation: Volume \(= \frac{\text{mass}}{\text{density}} = \frac{85}{1.7} = 50 \)cm\(^3\).

Mole & Mass MCQ's PDF

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