Determine the relative reactivity of calcium and magnesium by observing their reactions with dilute hydrochloric acid.

Practical Report: Determination of the Reactivity of Group 2 Metals

Title: WEEK 3 DETERMINATION OF THE REACTIVITY OF GROUP 2 METALS

Aim: To determine the relative reactivity of calcium and magnesium.

Apparatus and Materials:

1. Test tube
2. Test-tube rack
3. Dilute hydrochloric acid
4. Calcium
5. Magnesium

Introduction:
Metals in Group 2 of the Periodic Table are less reactive than those in Group 1. This experiment indicates the relative reactivity of elements within the group.

Precaution:
Wear eye protection.

Procedure:

1. Fill two test-tubes a quarter full with dilute hydrochloric acid.
2. Into one test-tube drop a very small piece of magnesium.
3. Into the other, drop a very small piece of calcium.
4. Compare the reactivity of the two metals.
5. Drop another bit of magnesium into the first test-tube and put your thumb over the end.
6. When the pressure can be felt, take your thumb off and test the gas with a lighted splint.
7. Record what happens.

Observation and Results:

Observation Point	Magnesium + Dilute HCl	Calcium + Dilute HCl
Initial reaction	Slow bubbling, magnesium slowly dissolves.	Vigorous bubbling, calcium dissolves rapidly.
Heat change	Slight temperature increase.	Significant temperature increase.
Gas test (Mg)	Gas collected produces a 'pop' sound with a lighted splint.	(Not tested in procedure, but would also be hydrogen)

Questions:

1. Which is the more reactive, magnesium or calcium?
Calcium is more reactive than magnesium.

2. Write word equations for these reactions.

• Magnesium + Hydrochloric acid $\longrightarrow$ Magnesium chloride + Hydrogen
• Calcium + Hydrochloric acid $\longrightarrow$ Calcium chloride + Hydrogen

3. Write formula equations for these reactions.

• For Magnesium: $$\text{Mg(s)} + 2\text{HCl(aq)} \longrightarrow \text{MgCl}_2\text{(aq)} + \text{H}_2\text{(g)}$$
• For Calcium: $$\text{Ca(s)} + 2\text{HCl(aq)} \longrightarrow \text{CaCl}_2\text{(aq)} + \text{H}_2\text{(g)}$$