Solution flash cards

1. 1.What is a solution?

   A homogeneous mixture of two or more chemically non-reacting substances whose composition can be varied within limits.

   Hint: Homogeneous mixture.

2. 2.Define solvent and solute in a binary solution.

   The component present in the largest amount is the solvent; the other component(s) present in smaller amount are the solute(s).

   Hint: Larger amount = solvent.

3. 3.What is a binary solution?

   A solution made of only two components — one solute and one solvent.

   Hint: Two components.

4. 4.List the three states a solution can exist in.

   Solid solutions, liquid solutions and gaseous solutions — depending on the physical state of the solvent.

   Hint: Based on solvent's state.

5. 5.Give an example of a gaseous solution (gas in gas).

   A mixture of oxygen and nitrogen gases (air).

   Hint: Air.

6. 6.Give an example of a solid in gas solution.

   Camphor (or iodine) vapour in nitrogen gas / air.

   Hint: Sublimed solid in gas.

7. 7.Give an example of a gas in liquid solution.

   Oxygen dissolved in water, or carbon dioxide dissolved in water (soda water).

   Hint: O2 in water.

8. 8.Give an example of a solid in liquid solution.

   Glucose or common salt dissolved in water.

   Hint: Sugar/salt water.

9. 9.Give an example of a liquid in solid solution.

   Amalgam of mercury with sodium (mercury dissolved in a solid metal).

   Hint: Amalgam.

10. 10.Give an example of a solid in solid solution.

    Metal alloys such as brass (copper and zinc) or bronze.

    Hint: Alloy.

11. 11.What is an aqueous solution?

    A solution in which water is the solvent.

    Hint: Solvent = water.

12. 12.Name the nine possible types of solutions based on the physical states of solute and solvent.

    Solute can be gas, liquid or solid and solvent can be gas, liquid or solid, giving $3\times 3 = 9$ types.

    Hint: 3 solute states × 3 solvent states.

13. 13.Why is concentration expressed rather than just 'amount of solute'?

    Because the properties of a solution depend on the relative amount of solute in a given amount of solvent or solution, i.e. on concentration.

    Hint: Relative amount matters.

14. 14.Define mass percentage (w/w).

    $\text{mass \%} = \dfrac{\text{mass of component}}{\text{total mass of solution}}\times 100$

    Hint: Mass of solute per 100 g solution.

15. 15.Define volume percentage (V/V).

    $\text{volume \%} = \dfrac{\text{volume of component}}{\text{total volume of solution}}\times 100$

    Hint: Common for liquid-liquid.

16. 16.Define mass by volume percentage (w/V).

    $\text{mass/volume \%} = \dfrac{\text{mass of solute (g)}}{\text{volume of solution (mL)}}\times 100$; used in medicine and pharmacy.

    Hint: g solute per 100 mL solution.

17. 17.What is parts per million (ppm)?

    $\text{ppm} = \dfrac{\text{mass of component}}{\text{total mass of solution}}\times 10^{6}$; used for very dilute (trace) concentrations.

    Hint: For trace amounts.

18. 18.Define mole fraction $x$.

    $x_A = \dfrac{n_A}{n_A + n_B}$, the ratio of moles of a component to the total moles. For a binary solution $x_A + x_B = 1$.

    Hint: Moles of component / total moles.

19. 19.Define molarity $M$ and its unit.

    $M = \dfrac{\text{moles of solute}}{\text{volume of solution in litres}}$; unit is $mol\,L^{-1}$.

    Hint: Moles per litre of solution.

20. 20.Define molality $m$ and its unit.

    $m = \dfrac{\text{moles of solute}}{\text{mass of solvent in kg}}$; unit is $mol\,kg^{-1}$.

    Hint: Moles per kg solvent.

21. 21.Which concentration terms are temperature independent and why?

    Mass percentage, mole fraction, molality and ppm — they involve masses (or moles) only, which do not change with temperature. Molarity depends on volume, which changes with temperature.

    Hint: Anything with volume varies with T.

22. 22.Why does molarity change with temperature but molality does not?

    Molarity uses volume of solution, and volume expands or contracts with temperature; molality uses mass of solvent, which is unaffected by temperature.

    Hint: Volume vs mass.

23. 23.Define normality $N$.

    $N = \dfrac{\text{gram equivalents of solute}}{\text{volume of solution in litres}}$.

    Hint: Gram equivalents per litre.

24. 24.What is solubility of a substance?

    The maximum amount of the substance that can be dissolved in a specified amount of solvent at a specified temperature to form a saturated solution.

    Hint: Max dissolved at given T.

25. 25.What is a saturated solution?

    A solution in which no more solute can dissolve at a given temperature; it is in dynamic equilibrium with undissolved solute.

    Hint: No more solute dissolves.

26. 26.State the general rule governing solubility.

    'Like dissolves like' — polar solutes dissolve in polar solvents and non-polar solutes dissolve in non-polar solvents.

    Hint: Like dissolves like.

27. 27.How does temperature affect the solubility of most solids in liquids?

    For endothermic dissolution ($\Delta H_{sol} > 0$) solubility increases with temperature; for exothermic dissolution ($\Delta H_{sol} < 0$) solubility decreases with temperature.

    Hint: Depends on sign of dissolution enthalpy.

28. 28.How does temperature affect the solubility of gases in liquids?

    Solubility of gases decreases with increasing temperature, because dissolution of a gas is exothermic.

    Hint: Warm water holds less gas.

29. 29.How does pressure affect the solubility of gases in liquids?

    Solubility of a gas increases with increase in the pressure of the gas above the solution.

    Hint: More pressure, more gas dissolves.

30. 30.State Henry's law.

    At constant temperature, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid.

    Hint: Solubility ∝ partial pressure.

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