Learning Lab

Exercises

1. How many millilitres of ethanol are required to prepare \(80\textrm{mL}\) of a \(70.0\%v/v\) solution?

Answer

\(56.0\textrm{mL}\)

2. A sodium chloride solution contains \(3.56\textrm{g}\) of sodium chloride dissolved in a final volume of \(25.0\textrm{mL}\). What is the percent concentration of sodium chloride in \(m/v\)?

Answer

\(14.2\%m/v\)

3. When \(2.50\textrm{g}\) of \(\ce{LiBr}\) is dissolved in \(25.0\textrm{g}\) of water, it gives a \(10.0\%m/m\) \(\ce{LiBr}\) solution. Calculate the mass of \(\ce{LiBr}\) present in \(15.0\textrm{g}\) of the same solution?

Answer

\(1.50\textrm{g}\)

4. How many grams of sodium chloride are required to prepare \(500\textrm{mL}\) of a \(2.0\%m/v\) sodium chloride solution?

Answer

\(10\textrm{g}\)

5. Brass is a metal alloy composed of \(\ce{Cu}\) and \(\ce{Zn}\). Usually, \(\ce{Cu}\) accounts for \(60.0\%m/m\) of the composition. What mass of the brass would contain \(48.3g\) of \(\ce{Cu}\)?

Answer

\(80.5\textrm{g}\)

6. Calculate the amount of solute or solvent required to prepare the following solution.

1. The Mass of \(\ce{K}_{2}\ce{SO}_{4}\) required to prepare \(48.0\textrm{g}\) of a \(3.00\%m/m\) \(\ce{K}_{2}\ce{SO}_{4}\) solution.
2. The volume of acetone required to prepare \(1.0\textrm{L}\) of a \(70.0\%v/v\) acetone solution.
3. The mass of sodium azide required to prepare \(500mL\) of \(1.50\%m/v\) a sodium azide solution.

Answer

1. \(1.44\textrm{g}\),
2. \(700\textrm{mL}\) or \(0.70\textrm{L}\),
3. \(7.50\textrm{g}\)

7. The maximum chlorine concentration allowed in drinking water is \(4.0\textrm{mg}\) per \(1.0\textrm{L}\left(1\textrm{kg}\right)\).
1. Express the maximum chlorine concentration in drinking water in ppm.
2. What is the maximum mass of chlorine allowed in \(240\textrm{mL}\left(240\textrm{g}\right)\) of drinking water?

Answer

1. \(4.0\textrm{ppm}\),
2. \(9.6\times10^{-4}\textrm{g}\) or \(0.96\textrm{mg}\)

8. Calculate the molarity of the following solutions:
1. \(3.0\textrm{mol}\) of Silver nitrate in \(0.50\textrm{L}\) of solution.
2. \(0.0625\textrm{mol}\) of Sodium bicarbonate in \(250.0\textrm{mL}\) of solution.

Answer

1. \(6.0\textrm{M}\),
2. \(0.250\textrm{M}\)

9. Calculate the mass in grams of the solute in each of the following solutions:
1. \(750.0\textrm{mL}\) of a \(1.50\textrm{M}\) \(\ce{NaOH}\) solution.
2. \(0.200\textrm{L}\) of a \(150.0\textrm{mM}\) \(\ce{NaCl}\) solution.
   Note: The molar masses of \(\ce{NaOH}\) and \(\ce{NaCl}\) are \(39.997\textrm{g/mol}\) and \(58.44\textrm{g/mol}\)

Answer

1. \(45.0\textrm{g}\),
2. \(1.75\textrm{g}\)

10. How many litres of a \(0.200\textrm{M}\) solution can be prepared from \(48.00\textrm{g}\) of each of the following solutes:
1. \(\ce{KCl}\).
2. \(\ce{NaNO}_{3}\).
   Note: The molar masses of \(\ce{KCl}\) and \(\ce{NaNO}_{3}\) are \(74.551\textrm{g/mol}\) and \(84.99\textrm{g/mol}\).

Answer

1. \(3.22\textrm{L}\)
2. \(2.82\textrm{L}\)

11. Calculate the molarity of a \(5.0\%\textrm{m/v}\) \(\ce{KOH}\) solution. Note: the molar mass of \(\ce{KOH}\) is \(56.1056\textrm{g/mol}\).

Answer

\(0.89\textrm{M}\)

12. How many millilitres of water should be added to a \(3.00\textrm{M}\) \(\ce{HCl}\) stock solution to yield \(100.0\textrm{mL}\) of \(1.00\textrm{M}\) \(\ce{HCl}\) solution?

Answer

\(66.7\textrm{mL}\)

13. A diluted \(\ce{NaOH}\) solution was prepared by adding \(100.0\textrm{mL}\) of water to the \(400.0\textrm{mL}\) of the \(0.1\textrm{M}\) stock solution. What is the molarity of the diluted \(\ce{NaOH}\) solution?

Answer

\(0.08\textrm{M}\)

14. What is the final volume of an \(\ce{H}_{2}\ce{SO}_{4}\) solution prepared from \(100.0\textrm{mL}\) of \(0.5000\textrm{M}\) \(\ce{H}_{2}\ce{SO}_{4}\) if the final concentration is \(0.1500\textrm{M}\)?

Answer

\(333.3\textrm{mL}\)

15. Rewrite: \(50.0\textrm{mL}\) of an \(\ce{NaOH}\) stock solution with a concentration of \(10.0\%m/v\) is diluted to \(250.0\textrm{mL}\). What is the final concentration of the \(\ce{NaOH}\) solution in \(m/v\%\)?

Answer

\(2.00\%m/v\)