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12.13Chapter 12: Chemical Reactions 3 and Rates

Chapter 12 Review: Chemical Reactions 3 and Rates — Alhussan Chemistry - Stage 9 Revision Notes & Topical Questions

5 min read 6 parts Lesson 13 of 13 1 quiz

📚 Alhussan Chemistry - Stage 9 Hub / Topical Revision
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Lesson summary

12.13 Chapter 12 Review: Chemical Reactions 3 and Rates — Alhussan International Academy — Chemistry (Stages 7–9) notes: Revise displacement and extraction, making soluble salts, and the factors that affect the rate of reaction.Displacement — a more reactive metal displaces a les…

  • Explaining
  • Excess metal
  • Evaporation
  • Other routes
  • Increase rate
  • Collisions

Section 1 of 6Displacement and extraction

Displacement
  • Displacement a more reactive metal displaces a less reactive one from a compound.
  • Zinc added to copper sulfate gives zinc sulfate and copper, so zinc is more reactive than copper.
  • Lead does not react with iron oxide, because lead is less reactive than iron.
Explaining
  • Explaining state which metal is more reactive and what is replaced.
Extraction
  • Extraction metals below carbon are reduced by heating with it, while those above carbon need electrolysis.

Section 2 of 6Making soluble salts

Excess metal
  • Excess metal add excess zinc to dilute hydrochloric acid, then filter off the unreacted zinc.
Evaporation
  • Evaporation pour the filtrate into an evaporating dish and heat over a water bath rather than directly.
  • Direct heating can make the solution spit or decompose the salt, whereas a water bath gives gentle, even heating at no more than 100 °C.
Equation
  • Equation zinc + hydrochloric acid → zinc chloride + hydrogen (Zn + 2HCl → ZnCl2 + H2).
  • Bubbles of gas form and the zinc gets smaller, and a lit splint gives a squeaky pop with hydrogen.
Hazards
  • Hazards dilute hydrochloric acid may cause irritation and zinc chloride crystals are corrosive, so eye protection is needed.
Other routes
  • Other routes metal oxide + acid → salt + water, and carbonate + acid → salt + water + carbon dioxide.

Section 3 of 6Rates of reaction

Increase rate
  • Increase rate higher concentration, higher temperature and larger surface area.
Collisions
  • Collisions collisions become more frequent, and for temperature they are also more energetic.
FactorEffect on rateExplanation
ConcentrationUpMore particles per volume
TemperatureUpFaster particles, more energetic collisions
Surface areaUpMore exposed particles
Rates of reaction
Calcium carbonate investigation
  • Calcium carbonate investigation the independent variable is the size of the pieces, the dependent variable is the time or gas volume,
    • and the controls are the mass, acid concentration and temperature.
    • (big lumps, small lumps, powder)
Graph
  • Graph label the axes with units;
    • curves level off at the same final volume, and the steeper start shows the faster rate.
Water bath
  • Water bath it keeps the temperature at or below 100 °C and heats evenly, but it does not make the reaction faster.

Section 4 of 6Practical skills

Practical questions
  • Practical questions name the apparatus and identify the variable changed, the variable measured and those controlled.
Balancing equations
  • Balancing equations count atoms on both sides, and include state symbols if requested.
Calculations
  • Calculations show working and give units.

Section 5 of 6Key terms

TermMeaning
Displacementa more reactive metal replacing a less reactive one.
Evaporating disha shallow dish used to evaporate solutions.
Ratethe speed of a reaction.
Water batha container of hot water used for gentle heating.
Limiting reactantthe reactant that is used up first.

Section 6 of 6Exam technique

1
Saying the water bath makes the reaction faster — it gives gentle, even heating.
2
Forgetting that excess metal is filtered off — the unreacted metal is removed by filtration.
3
Saying concentration changes the final volume of gas when the acid is in excess — the final volume depends on the limiting reactant.
4
Mixing up independent and dependent variables — the independent variable is changed and the dependent variable is measured.

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