Mixed Stoichiometry I Answer Key (CHEM 1405)

Back to Chemistry 1405 Practice Problems

 

Mg      +      2HCl            MgCl₂      +      H₂

Provide the mole ratio for each of the following mole conversions:

1. Mg to H₂:  $(\frac{1molMg}{1molH_2})$ or $(\frac{1molH_2}{1molMg})$ 
   
   
2. HCl to H₂:   $(\frac{2molHCl}{1molH_2})$ or $(\frac{1molH_2}{2molHCl})$ 
   
   
3. Mg to HCl:   $(\frac{1molMg}{2molHCl})$ or $(\frac{2molHCl}{1molMg})$ 
   
   
4. MgCl₂ to HCl:   $(\frac{1molMgCl_2}{2molHCl})$ or $(\frac{2molHCl}{1molMgCl_2})$ 

 

 

Ca₃P₂(s) + 6H₂O(l)  3Ca(OH)₂(s) + 2PH₃(g)

5. How many moles of phosphine (PH₃) are prepared from 5.00 moles of Ca₃P₂ ?

 $5.00molCa_3P_2\times(\frac{2molPH_3}{1molCa_3P_2})=$ 10.0 mol PH₃

 

6. How many moles of phosphine (PH­₃) are prepared from 5.00 moles of H₂O?

 $5.00molH_2O\times(\frac{2molPH_3}{6molH_2O})=$ 1.67 mol PH₃

 

 

C₃H₈      +      5O₂            3CO₂      +      4H₂O

7. How many moles of CO₂ are produced from the combustion of 45 g of C₃H₈?

$45gC_3H_8\times(\frac{1molC_3H_8}{44.11gC_3H_8})\times(\frac{3molCO_2}{1molC_3H_8})=$ 3.06 mol CO₂

 

8. What mass of H₂O is produced if 0.200 mole of CO₂ is also produced?

$0.200molCO_2\times(\frac{4molH_2O}{3molCO_2})\times(\frac{18.02gH_2O}{1molH_2O})=$ 4.81g H₂O

 

9. What mass of C₃H₈ is required to produce 1.80 g of H₂O?

$1.80gH_2O\times(\frac{1molH_2O}{18.02gH_2O})\times(\frac{1molC_3H_8}{4molH_2O})\times(\frac{44.11gC_3H_8}{1molC_3H_8})=$ 1.10g C₃H₈

 

10. What mass of C₃H₈ is required to react with 160 g of O₂?

$160gO_2\times(\frac{1molO_2}{32.00gO_2})\times(\frac{1molC_3H_8}{5molO_2})\times(\frac{44.11gC_3H_8}{1molC_3H_8})=$ 44g C₃H₈