# Something with A Twist

```Solution Stoichiometry:
Something with a Twist
1. During the developing process of black and white film, silver bromide is removed from photographic film
by the fixer. The major component of the fixer is sodium thiosulfate. The net ionic equation for the
reaction is: AgBr + 2 S2O32Ag(S2O3)3- + Br- .
What mass of AgBr can be dissolved by 1.00L of 0.200M Na2S2O3?
2. Calculate the volume of a 0.156M CuSO4 solution that would react with 7.89g of zinc. Hint: Write a
balanced equation for this single replacement reaction.
3. A 6.77g sample of a mixture was analyzed for barium ions by adding a small excess of sulfuric acid to an
aqueous sample. The resultant reaction produced a precipitate of barium sulfate which was collected by
filtration, wash, dried and weighed. If 0.4123g of barium sulfate was obtained, what was the mass
percent of barium in the sample? Hint: Write the net ionic equations for the precipitate reaction.
4. A useful application of oxalic acid is the removal of rust, Fe2O3, from bathtub rings according to the
reaction: Fe2O3 + 6 H2C2O4
2 Fe(C2O4)33- + 3 H2O + 6 H+ Calculate the number of grams of
rust that can be removed by 500ml of a 0.100M solution of oxalic acid.
5. If 100.0ml of a 0.25M AgNO3 is reacted with 125ml of 0.15M KBr, how many grams of AgBr will form?
6. If you want a 150ml of a 5.0M solution of HBr, how would you prepare the solution from a HBr solution
of 12.0M
7. Laws passed in some states define a drunk driver as one who drives with a blood alcohol level of 0.10%
by mass or higher. The level of alcohol can be determined by titrating blood plasma with potassium
dichromate according to the equation:
16 H+ + 2 Cr2O72- + C2H5OH
4 Cr3+ + 2 CO2 + 14 H2O
Assuming that the only substance that reacts with the dichromate in blood plasma is alcohol, is a person
legally drunk if 38.49ml of 0.723M potassium dichromate is required to titrate a 50.0 gram sample of
blood plasma?
8. Laundry bleach is a solution of sodium hypochlorite. To determine the hypochlorite, ClO-, content of
bleach, sulfide ion is added in basic solution. The balanced equation for the reaction is:
ClO- + S2- + H2O
Cl- + S + 2OHThe chloride ion resulting from the reduction of HClO is precipitated as AgCl. When 50.0ml of laundry
bleach (d=1.02g/ml) is treated as described above, 4.95g of AgCl is obtained. What is the mass percent
of NaClO in bleach?
```