3RD QUARTER S.Y.2017: Stoichiometry Reviewer (SORT OF EASY)

SORT OF EASY STOICHIOMETRY PROBLEMS

1)  Chlorine is used by textile manufacturers to bleach cloth.  Excess chlorine is destroyed by its reaction with sodium thiosulfate, Na₂S₂O₃:

Na₂S₂O_3(aq) + 4Cl_2(g) + 5H₂O_(aq) à 2NaHSO_4(aq) + 8HCl_(aq)

a.     How many moles of Na₂S₂O₃ are needed to react with 0.12mol of Cl₂?

b.     How many moles of HCl can form from 0.12mol of Cl₂?

c.       How many moles of H₂O are required for the reaction of 0.12mol of Cl₂?

d.     How many moles of H₂O react if 0.24mol HCl is formed?

2)  The incandescent white of a fireworks display is caused by the reaction of phosphorous with O₂ to give P₄O₁₀.

a.     Write the balanced chemical equation for the reaction.

b.     How many grams of O₂ are needed to combine with 6.85g of P?

c.       How many grams of P₄O₁₀ can be made from 8.00g of O₂?

d.     How many grams of P are needed to make 7.46g P₄O₁₀?

3)  In dilute nitric acid, HNO₃, copper metal dissolves according to the following equation:

3Cu_(s) + 8HNO_3(aq) à 3Cu(NO₃)_2(aq) + 2NO_(g) + 4H₂O_(aq)

            How many grams of HNO₃ are needed to dissolve 11.45g of Cu?

4)  The reaction of powdered aluminum and iron(II)oxide,

2Al_(s) + Fe₂O_3(s) à Al₂O_3(s) + 2Fe_(l)

produces so much heat the iron that forms is molten.  Because of this, railroads use the reaction to provide molten steel to weld steel rails together when laying track.  Suppose that in one batch of reactants 4.20mol Al was mixed with 1.75mol Fe₂O₃.

a.     Which reactant, if either, was the limiting reactant?

b.     Calculate the mass of iron (in grams) that can be formed from this mixture of reactants.

5)  Silver nitrate, AgNO₃, reacts with iron(III) chloride, FeCl₃, to give silver chloride, AgCl, and iron(III) nitrate, Fe(NO₃)₃.  A solution containing 18.0g AgNO₃ was mixed with a solution containing 32.4g FeCl₃. How many grams of which reactant remains after the reaction is over?

ANSWERS:

1)  a. 0.030mol Na₂S₂O₃            b. 0.24mol HCl            c. 0.15mol H₂O

 d. 0.15mol H₂O

2)  a. 4P + 5O₂ à P₄O₁₀            b. 8.85g O₂            c. 14.2g P₄O₁₀               d. 3.26g P

3)  30.31g HNO₃

4)  a. limiting reactant is Fe₂O₃            b. 195g Fe is formed

5)  26.7g of FeCl₃ are left over