THE QUESTIONS:
1. Consider the reaction: 2 Na + 2 H2O à
2 NaOH + H2(g)
a. If 13.02 g of Na is thrown into a lake and completely
reacted, and a total of 3.90 L of H2 are produced at STP, what is
the percent purity of the Na?
b. What mass (in grams) of Na would be required to produce
2.895 L of H2 at STP, if the Na has a purity of 43.60%?
2. Consider the reaction: 8 H2S(g) + 4 O2
à
S8 + 8 H2O
a. If 1.000 L of H2S reacts with excess O2
at STP, and 1.324 g of S8 are produced, what is the percentage yield
of the reaction?
b. What is the volume (in litres) of O2 required
to produce 4.25 g of H2O at STP, if the reaction has a 83.0% yield?
3. Consider the reaction: N2(g) + O2(g)
+ Br2(g) à 2 NOBr(g)
If 3.509 g of N2, 3.089 L of O2, and
23.71 g of Br2 are mixed together in a large vessel,
a. Which chemical is the limiting reactant?
b. How much NOBr (in litres) can be produced, if the
reaction proceeds to completion?
c. What mass (in grams) of the excess reactants are left
over after the reaction?
4. Consider the reaction: H2SO4 + 2
NaOH à
Na2SO4 + 2 H2O
A simple neutralization is carried out using a bottle of H2SO4,
having a concentration of 64.0% by weight and claiming to have 95.00% purity.
If 10.00 g of the H2SO4 solution is reacted with excess NaOH,
and 8.708 g of Na2SO4 is produced, is the label accurate
in claiming to have 95.00% purity? If not, what is the purity of the H2SO4
solution?
THE ANSWERS:
1 a. 61.4%
1 b. 13.28 g Na (impure)
2 a. 92.48%
2 b. 3.18 L O2
3 a. N2 is limiting
3 b. 5.614 L NOBr
3 c. 0.403 g O2; 3.6836 g Br2
4. The label is not accurate in claiming 95.00% purity; The purity of the solution is 93.90%.
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