2.1.6Inorganic Chemistry: Part 1
Practical: Investigate Metals Reacting with Acids — Edexcel International GCSE Science Double Award (Modular) - Chemistry Unit 1 Revision Notes & Topical Questions
5 min read 6 parts Lesson 7 of 15
Part 1 of 4Aim and variables
Aim
- Aim To compare how magnesium, zinc and iron react with dilute hydrochloric acid and dilute sulfuric acid.
Variables
- Variables The independent variable is the type of metal;
- the dependent variable is how vigorously it reacts (bubbling rate, heat, time to dissolve).
- Control the acid volume, concentration, temperature and the size or surface area of each metal sample.
Safety
- Safety Wear eye protection throughout because acid splashes damage eyes.
- Keep flames away from the hydrogen being produced except when carrying out the splint test on a small sample.
Part 2 of 4Method
1
Use a small measuring cylinder to put about 5 cm3 of dilute hydrochloric acid into each of three test tubes in a rack.
2
Add a piece of magnesium ribbon about 1 cm long to the first tube and record what you see.
3
Hold a lighted splint at the mouth of the tube to test any gas given off.
4
Add iron filings to the second tube and zinc granules to the third, then observe and test for gas in the same way.
5
Rinse out the tubes and repeat the whole experiment with dilute sulfuric acid.
6
Record all observations in a results table.
Part 3 of 4Typical results
| Metal | With hydrochloric acid | With sulfuric acid |
|---|---|---|
| Magnesium | Dissolves quickly, tube warms, gas pops with a lighted splint, colourless solution remains | Rapid bubbling, splint pops, metal dissolves |
| Zinc | Steady bubbles, metal slowly dissolves | Gas given off slowly, metal dissolves to a colourless solution |
| Iron | Very slow bubbling | Slow reaction with small bubbles |
Part 4 of 4Conclusions and equations
Mg, Zn, Fe in order
Order of reactivity
- Order of reactivity Magnesium reacts fastest, then zinc, then iron, so the reactivity order is magnesium, zinc, iron.
Products
- Products With each acid, the products are a salt solution and hydrogen gas.
- Hydrogen is confirmed by the squeaky pop with a lighted splint.
Equations
- Equations Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
- Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g)
- Fe(s) + 2HCl(aq) → FeCl2(aq) + H2(g)
Key terms
| Term | Meaning |
|---|---|
| Dilute acid | An acid with a low concentration of acid dissolved in water. |
| Lighted splint | A burning wooden splint used to test for hydrogen gas. |
| Surface area | The total area of metal exposed to the acid; a bigger area speeds up a reaction. |
| Dependent variable | The quantity measured to see the effect of the change. |
| Salt solution | The solution of a metal chloride or sulfate left after the metal reacts. |
Avoid these mistakes
1
Using different sizes of metal pieces, so the comparison is unfair because the surface area is not controlled.
2
Describing the test for hydrogen as a glowing splint relighting; that is the test for oxygen. Hydrogen gives a squeaky pop with a lighted splint.
3
Saying the metal 'melts' in acid. It reacts and dissolves to form a salt.
4
Forgetting that the reaction with sulfuric acid gives a sulfate while hydrochloric acid gives a chloride.
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