Test Yourself 3.2:
[Relative atomic mass: H = 1, C = 12, N = 14, O = 16, Na = 23, Cl = 35.5, K = 39, Fe = 56, Pb = 207; Avogadro constant, NA: 6.02 × 1023 mol–1; Molar volume: 22.4 dm3 mol–1 at STP or 24 dm3 mol–1 at room conditions]
1. Calculate the molar mass of each of the following substances:
(a) Lead metal, Pb
(b) Chloroform, CHCl3
(c) Sodium nitrate, NaNO3
(d) Iron(III) oxide, Fe2O3
2. Calculate the number of molecules found in 8 mol of water.
3. What is the mass of 0.5 mol of ammonia, NH3?
4. How many moles of K2O units are found in 14.1 g of potassium oxide, K2O?
5. Calculate the volume of 16 g of oxygen gas, O2 at STP.
6. The mass of 4 dm3 of a gas is 12 g at room conditions. Calculate the molar mass of the gas.
7. 4 g of hydrogen gas, H2 has greater number of molecules than 14 g of nitrogen gas, N2.
Do you agree with the above statement? Give your reason.
Answer:
1. (a) 207 g mol-1
(b) 119.5 g mol-1
(c) 85 g mol-1
(d) 160 g mol-1
2. 4.816 × 1024 molecules
3. 8.5 g
4. 0.15 mol
5. 11.2 dm3
6. 72 g mol-1
7. Yes. 4 g of hydrogen gas contains 2 mol of hydrogen gas, that is 1.204 × 1024 molecules H2. 14 g of nitrogen gas contains 0.5 mol nitrogen gas, that is 3.01 × 1023 N2 molecules.
[Relative atomic mass: H = 1, C = 12, N = 14, O = 16, Na = 23, Cl = 35.5, K = 39, Fe = 56, Pb = 207; Avogadro constant, NA: 6.02 × 1023 mol–1; Molar volume: 22.4 dm3 mol–1 at STP or 24 dm3 mol–1 at room conditions]
1. Calculate the molar mass of each of the following substances:
(a) Lead metal, Pb
(b) Chloroform, CHCl3
(c) Sodium nitrate, NaNO3
(d) Iron(III) oxide, Fe2O3
2. Calculate the number of molecules found in 8 mol of water.
3. What is the mass of 0.5 mol of ammonia, NH3?
4. How many moles of K2O units are found in 14.1 g of potassium oxide, K2O?
5. Calculate the volume of 16 g of oxygen gas, O2 at STP.
6. The mass of 4 dm3 of a gas is 12 g at room conditions. Calculate the molar mass of the gas.
7. 4 g of hydrogen gas, H2 has greater number of molecules than 14 g of nitrogen gas, N2.
Do you agree with the above statement? Give your reason.
Answer:
1. (a) 207 g mol-1
(b) 119.5 g mol-1
(c) 85 g mol-1
(d) 160 g mol-1
2. 4.816 × 1024 molecules
3. 8.5 g
4. 0.15 mol
5. 11.2 dm3
6. 72 g mol-1
7. Yes. 4 g of hydrogen gas contains 2 mol of hydrogen gas, that is 1.204 × 1024 molecules H2. 14 g of nitrogen gas contains 0.5 mol nitrogen gas, that is 3.01 × 1023 N2 molecules.