Answers to the additional practice problems

(Modified from Exercise 8) - Gram-mole Practice Problems

1. What is the weight of 0.30 mole of sulfur?  9.6 g

 2. What is the weight of 5.5 mole of silicon?  150 g (only 2 sig. dig.)

 3. How many moles are there in 45 g of Cl?  1.3 mol

 4. Change 34 g of lithium to moles.  4.9 mol

 5. What is the weight of 4.30 mole of sodium?  98.9 g

 6. What is the weight of 1.75 mole of Ca?  70.1 g

 7. How many moles are there in 85.3 g of P?  2.75 mol

 8. Change 0.566 g of silver to moles.  .00525 mol

(Modified from Exercise 13) - Practice Calculating Formula Weights

1. HCl  36.46 g/mol

2. SiH₄   32.13 g/mol

3. C₃H₆O₂   74.09 g/mol

4. Fe(NO₃)₃   241.88 g/mol

5. NaCl   58.44 g/mol

6. CaSO₄   136.15 g/mol

7. C₂H₄O₂   60.06 g/mol

8. Sn(CO₃)₂   238.73 g/mol

(Modified from Exercise 14) - Gram-mole Practice Problems

1. Change 3.4 moles of HCl to grams.  120 g

 2. Change 8.5 g of SiH₄ to moles.  .26 mol

 3. Change 5.20 moles of C₃H₆O₂ to grams.  385 g

 4. Change 13.2 g of Fe(NO₃)₃ to moles.  .0546 mol

 5. Change 3.4 moles of NaCl to grams.  2.0x10² g

 6. Change 8.5 g of CaSO₄ to moles.  .062 mol

 7. Change 5.20 moles of C₂H₄O₂ to grams.  312 g

 8. Change 13.2 g of Sn(CO₃)₂ to moles.  .0553 mol

(Modified from Exercise 17) - Practice Calculating Composition From Formula

1. SO₂  50.05% S and 49.95% O

2. Na₂CO₃  43.38% Na, 11.33% C, and 45.29% O

3. FeCO₃  48.20% Fe, 10.37% C, and 41.43% O

4. CH₂O  39.99% C, 6.73% H, and 53.28% O

5. CaCO₃  40.04% Ca, 12.00% C, and 47.96% O

6. Fe(OH)₃  52.25% Fe, 44.91% O, and 2.83% H

 (Modified from Exercise 19) - Practice Determining Empirical Formulas

1. Calculate the empirical formula of the compound that contains 1.0 g S for each 1.5 g O.  SO₃

2. Calculate the empirical formula of the compound containing 75.0% C and 25.0% H.  CH₄

3. Calculate the empirical formula of the compound containing 81.8% C and 18.2% H.  C₃H₈

4. Determine the empirical formula of the compound containing 37.5% C, 12.5% H, and 50.0% O by weight.  CH₄O

5. Determine the empirical formula of the compound containing 26.1% C, 4.3% H, and 69.6% O by weight.  CH₂O₂

6. Determine the empirical formula of the compound containing 38.7% C, 16.1% H, and 45.2% N by weight.  CH₅N

7. What is the empirical formula of a compound if a 50.0 g sample of it contains 9.1 g Na, 20.6 g Cr, and 22.2 g O?  Na₂Cr₂O₇

(Modified from Exercise 21) - Practice Determining Molecular Formulas

1. Empirical formula C₃H₇, molecular weight 86  C₆H₁₄

2. Empirical formula S, molecular weight 256  S₈

3. Empirical formula CH, molecular weight 26  C₂H₂

4. Empirical formula NO₂, molecular weight 46  NO₂

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