CHEMISTRY · Stage 9 · Chapter 12: Chemical Reactions 3 and Rates
Chemistry 12.13 Chapter 12 Review: Chemical Reactions 3 and Rates
5 min read 4 parts Lesson 13 of 13
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 4Displacement and extraction
- 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
- state which metal is more reactive and what is replaced.
- Extraction
- metals below carbon are reduced by heating with it, while those above carbon need electrolysis.
Section 2 of 4Making soluble salts
- Excess metal
- add excess zinc to dilute hydrochloric acid, then filter off the unreacted zinc.
- 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
- 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
- dilute hydrochloric acid may cause irritation and zinc chloride crystals are corrosive, so eye protection is needed.
- Other routes
- metal oxide + acid → salt + water, and carbonate + acid → salt + water + carbon dioxide.
Section 3 of 4Rates of reaction
- Increase rate
- higher concentration, higher temperature and larger surface area.
- Collisions
- collisions become more frequent, and for temperature they are also more energetic.
| Factor | Effect on rate | Explanation |
|---|---|---|
| Concentration | Up | More particles per volume |
| Temperature | Up | Faster particles, more energetic collisions |
| Surface area | Up | More exposed particles |
- 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)
- the independent variable is the size of the pieces, the dependent variable is the time or gas volume,
- Graph
- label the axes with units; curves level off at the same final volume, and the steeper start shows the faster rate.
- 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 4Practical skills
- Practical questions
- name the apparatus and identify the variable changed, the variable measured and those controlled.
- Balancing equations
- count atoms on both sides, and include state symbols if requested.
- Calculations
- show working and give units.
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