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E. Solutions and Solubility · Solutions and Solubility

Solutions and Solubility: Unit Review

A1.2 A1.4 A1.5 A1.6 A1.8 A1.9 A1.10 A1.12 A1.13 A2.1 A2.2 E1.1 E1.2 E2.1 E2.2 E2.3 E2 E2.5 E2.6 E2.7 E2.8 E3.1 E3.2 E3.3 E3.4 E3.5 E3.6About 40 minutes
Learning goals
  • I can explain the properties of water and how substances dissolve.
  • I can calculate and convert concentrations, and prepare and dilute solutions.
  • I can predict precipitates, write net ionic equations and solve solution stoichiometry and titration problems.
  • I can explain acids and bases with the Arrhenius theory, calculate pH and compare strong and weak acids.
  • I can analyse water pollution and drinking-water issues using evidence and Canadian standards.

Words to know

solubility
The maximum amount of solute that dissolves in a given amount of solvent at a stated temperature.
molar concentration
c = n ÷ V, in mol/L.
net ionic equation
An equation showing only the particles that change; spectator ions are left out.
pH
pH = −log[H₃O⁺].
strong acid
An acid that ionizes completely in water.
equivalence point
The point in a titration where acid and base are present in exactly the mole ratio of the equation.

Let's review!

In this unit you started with water itself: a bent, polar molecule held together by hydrogen bonds. You used that to explain how ionic, polar and non-polar substances dissolve, what solubility means, and how temperature and pressure change it. You learned to express concentration in percent, ppm, ppb and mol/L, to prepare and dilute solutions, and to use the solubility table, net ionic equations and solution stoichiometry. You explained acids and bases with the Arrhenius theory, calculated pH, compared strong and weak acids, and found the acid in vinegar by titration. Finally, you applied it all to water pollution and safe drinking water.

This review has a few questions from every lesson. Try each one, then press Show answer to check.

How to use this review

Work through one or two sections at a time with a calculator and the solubility table beside you. For every calculation, write the formula, substitute with units, and round only at the end. For every question you get wrong, write down why (wrong formula? mL instead of L? forgot the mole ratio? split a solid into ions?) and go back to that lesson's worked examples. The parent notes below say which lesson to revisit for each kind of mistake. Finish with the 10-question quiz.

SolutionsWater and dissolvingpolarity, H bondslike dissolves likeT and P effectsConcentration%, ppm, ppbc = n/Vc₁V₁ = c₂V₂Reactions in solutionsolubility tablenet ionic equationsstoichiometryAcids and basesArrhenius, pH, strong/weaktitrationWater and societypollution, cumulative effectstreatment, standards
The big ideas of the unit and how they connect. Every topic rests on what water is and how it dissolves things.
% m/mm solute ÷ m solution × 100%% m/vm solute (g) ÷ V solution (mL) × 100%ppm ≈ mg/Lm solute ÷ m solution × 10⁶c (mol/L)c = n ÷ V, n = m ÷ Mdilutionc₁V₁ = c₂V₂ (V₂ = total)pHpH = −log[H₃O⁺], [H₃O⁺] = 10⁻ᵖᴴ% ionization[H₃O⁺] ÷ c(acid) × 100%
The key formulas of the unit on one card. Always use the volume of solution, and litres in c = n ÷ V.
Just for fun

By the end of this unit you can explain why ice floats, why a warm soda goes flat, how much acid is in your vinegar and what happens to the water you flush. That's a lot of chemistry for something that just looks like a glass of water.

Water: A Polar Molecule with Hydrogen Bonds

1

Explain why water is polar but carbon dioxide is not.

2

What is a hydrogen bond? Is it broken when water boils?

3

Why does ice float, and why does that matter to lake ecosystems in winter?

Solutions, Solubility and Saturation

1

Name the solute and solvent in brass.

2

Solubility of NaCl is 36.0 g/100 mL at 20 °C. Describe 45.0 g NaCl in 100 mL water at 20 °C.

3

Does stirring change solubility? Explain.

How Ionic, Polar and Non-polar Substances Dissolve

1

Write the dissociation equation for aluminium nitrate.

2

Is glucose an electrolyte? Explain.

3

Predict: does wax dissolve better in water or in hexane?

How Temperature and Pressure Affect Solubility

1

A saturated KNO₃ solution in 100 g of water is cooled from 60 °C (110 g) to 40 °C (63.9 g). Mass of crystals?

2

How does warming water affect dissolved oxygen? Why does this matter?

3

Why does opening a soda bottle cause bubbles?

Concentration I: Percent, g/100 mL, ppm and ppb

1

8.0 g of sugar in 192.0 g of water: % m/m?

2

Express 0.012 mg/L as ppb.

3

What mass of NaCl is in 250 mL of 0.90% m/v saline?

Concentration II: Molar Concentration (mol/L)

1

2.92 g of NaCl (58.44 g/mol) in 500.0 mL of solution: concentration?

2

Find [Cl⁻] in 0.25 mol/L AlCl₃.

3

What mass of KOH (56.11 g/mol) is needed for 250.0 mL of 0.400 mol/L?

Preparing Standard Solutions and Dilutions

1

What volume of 6.0 mol/L HCl is needed to make 500 mL of 0.30 mol/L?

2

Why is the beaker rinsed into the volumetric flask?

3

Why add acid to water and not the reverse?

Water Pollution: Sources and Cumulative Effects

1

Classify as point or non-point: (a) landfill leachate pipe, (b) road salt runoff.

2

Explain biomagnification using mercury in walleye.

3

How does extra phosphorus lead to fish deaths?

The Solubility Table, Precipitates and Testing for Ions

1

Is Ba(OH)₂ high or low solubility? Is BaSO₄?

2

Predict the precipitate: Na₂CO₃(aq) + CaCl₂(aq).

3

How would you test a solution for chloride ions?

Total and Net Ionic Equations

1

Write the net ionic equation for KOH(aq) + HBr(aq).

2

Write the net ionic equation for Pb(NO₃)₂(aq) + Na₂SO₄(aq).

3

Name the spectator ions in the last question.

Solution Stoichiometry

1

What volume of 0.200 mol/L NaOH neutralizes 30.0 mL of 0.100 mol/L H₂SO₄?

2

Excess Na₂SO₄ precipitates 0.467 g BaSO₄ (233.40 g/mol) from 20.0 mL of BaCl₂. Find [BaCl₂].

3

Theoretical yield 3.20 g, actual 2.88 g. Percentage yield?

Arrhenius Acids and Bases, Hydronium and pH

1

Write the reaction of HCl with water using the modified Arrhenius theory.

2

pH of 0.0050 mol/L HNO₃?

3

[H₃O⁺] at pH 4.70?

Strong and Weak Acids and Bases

1

Distinguish 'strong' from 'concentrated'.

2

0.10 mol/L of a weak acid has pH 3.00. Percentage ionization?

3

Which needs more NaOH to neutralize: 20 mL of 0.1 mol/L HCl or 20 mL of 0.1 mol/L acetic acid?

Acid-Base Titration: How Much Acetic Acid Is in Vinegar?

1

Why is phenolphthalein used for vinegar + NaOH?

2

5.00 mL of vinegar needs 8.50 mL of 0.500 mol/L NaOH. Find [CH₃COOH].

3

Overshooting the endpoint makes the calculated acid concentration too high or too low?

Safe Drinking Water: Treatment, Standards and Choices

1

What does alum do in water treatment?

2

A tap sample has 7 µg/L lead. Does it meet the 0.005 mg/L MAC?

3

Name one change in Ontario after the Walkerton tragedy.

Check your understanding

Quiz

1.

Why is water a good solvent for ionic compounds?

2.

For most solids, raising temperature ___; for gases, it ___ solubility.

3.

0.0080 mg/L of a metal is

4.

What is the concentration of 0.30 mol of NaCl in 1.5 L of solution?

5.

50.0 mL of 0.400 mol/L KCl is diluted to 200.0 mL. New concentration:

6.

Which pair forms a precipitate when mixed?

7.

The net ionic equation for BaCl₂(aq) + K₂SO₄(aq) is

8.

The pH of 0.0010 mol/L HCl is

9.

A weak acid is one that

10.

10.00 mL of vinegar needs 15.00 mL of 0.600 mol/L NaOH. [CH₃COOH] is

For parents and teachers

How to use this review: let your teen work through each section with a calculator and the solubility table, then check the answers together. Use the patterns of mistakes to choose which lesson to revisit:

  • Explaining dissolving, polarity, hydrogen bonds: revisit Water: A Polar Molecule with Hydrogen Bonds and How Ionic, Polar and Non-polar Substances Dissolve.
  • Saturated/unsaturated, reading solubility curves, gas solubility: Solutions, Solubility and Saturation and How Temperature and Pressure Affect Solubility.
  • Percent, ppm, ppb, unit conversions (mg, µg): Concentration I.
  • c = n/V errors, mL vs L, ion concentrations: Concentration II.
  • Dilution (using water added instead of total volume), lab procedure: Preparing Standard Solutions and Dilutions.
  • Predicting precipitates, ion tests: The Solubility Table, Precipitates and Testing for Ions.
  • Splitting solids, water or weak acids into ions; spectators: Total and Net Ionic Equations.
  • Missing the mole ratio, limiting reagent, percentage yield: Solution Stoichiometry (and the Quantities in Chemical Reactions unit for mole skills).
  • pH calculations, hydronium, why ammonia is a base: Arrhenius Acids and Bases, Hydronium and pH.
  • Strength vs concentration, percentage ionization: Strong and Weak Acids and Bases.
  • Titration calculations, indicators, error analysis: Acid-Base Titration.
  • Pollution sources, cumulative effects, drinking-water standards and issues: Water Pollution and Safe Drinking Water.

Encourage your teen to explain answers aloud; explaining is the best test of understanding. The unit connects forward to SCH4U (equilibrium, Ka, Ksp and pH of bases).