Chemistry » Acid-Base and Redox Reactions » Acid-Base Reactions

# Acid and a Metal Carbonate

## Optional Experiment: The reaction of acids with carbonates

### Apparatus and materials

• Small amounts of baking powder (sodium bicarbonate)
• hydrochloric acid (dilute) and vinegar
• retort stand
• two test tubes
• one rubber stopper for the test tube
• a delivery tube
• lime water (calcium hydroxide in water)

The experiment should be set up as shown below.

### Method

1. Carefully stick the delivery tube through the rubber stopper.

2. Pour limewater into one of the test tubes.

3. Carefully pour a small amount of hydrochloric acid into the other test tube.

4. Add a small amount of sodium carbonate to the acid and seal the test tube with the rubber stopper. Place the other end of the delivery tube into the test tube containing the lime water.

5. Observe what happens to the colour of the limewater.

6. Repeat the above steps, this time using vinegar.

### Observations

The clear lime water turns milky meaning that carbon dioxide has been produced. You may not see this for the hydrochloric acid as the reaction may happen to fast.

When an acid reacts with a metal carbonate a salt, carbon dioxide and water are formed. Look at the following examples:

• Nitric acid reacts with sodium carbonate to form sodium nitrate, carbon dioxide and water.

$2\text{HNO}_{3}\text{(aq)} + \text{Na}_{2}\text{CO}_{3}\text{(aq)} \rightarrow 2\text{NaNO}_{3}\text{(aq)} + \text{CO}_{2}\text{(g)} + \text{H}_{2}\text{O (l)}$

• Sulfuric acid reacts with calcium carbonate to form calcium sulfate, carbon dioxide and water.

$\text{H}_{2}\text{SO}_{4}\text{(aq)} + \text{CaCO}_{3}\text{(aq)} \rightarrow \text{CaSO}_{4}\text{(s)} + \text{CO}_{2}\text{(g)} + \text{H}_{2}\text{O (l)}$

• Hydrochloric acid reacts with calcium carbonate to form calcium chloride, carbon dioxide and water.

$2\text{HCl (aq)} + \text{CaCO}_{3}\text{(s)} \rightarrow \text{CaCl}_{2}\text{(aq)} + \text{CO}_{2}\text{(g)} + \text{H}_{2}\text{O (l)}$

Using what we have learnt about acids and bases we can now look at preparing some salts.

## Optional Experiment: Making salts

### Aim

To make some salts using acid-base reactions.

### Materials

• hydrochloric acid ($$\text{1}$$ $$\text{mol·dm^{-3}}$$), sulfuric acid (dilute), sodium hydroxide, copper(II) oxide, calcium carbonate

• beakers, mass meter, funnels, filter paper, bunsen burner, measuring cylinders

### Method

#### Warning:

Wear gloves and safety glasses when working with sulfuric acid. Work in a well ventilated room.

Part 1

1. Measure out $$\text{20}$$ $$\text{ml}$$ of hydrochloric acid into a beaker.
2. Measure out $$\text{20}$$ $$\text{ml}$$ of sodium hydroxide and carefully add this to the beaker containing hydrochloric acid.
3. Gently heat the resulting solution until all the water has evaporated. You should have a white powder left.

Part 2

1. Carefully add $$\text{25}$$ $$\text{ml}$$ of sulfuric acid to a clean beaker.
2. Add about a small amount (about $$\text{0.5}$$ $$\text{g}$$) of copper(II) oxide to the beaker containing sulfuric acid. Stir the solution.
3. Once all the copper(II) oxide has dissolved, add another small amount of copper(II) oxide. Repeat until no more solid dissolves and there is a small amount of undissolved solid.
4. Filter this solution and discard the filter paper.
5. Gently heat the resulting liquid. You should get a small amount of solid.

Part 3

1. Measure out $$\text{20}$$ $$\text{ml}$$ of hydrochloric acid into a new beaker.
2. Add about a small amount (about $$\text{0.5}$$ $$\text{g}$$) of calcium carbonate to the beaker containing hydrochloric acid. Stir the solution.
3. Once all the calcium carbonate has dissolved, add another small amount of calcium carbonate. Repeat until no more solid dissolves and there is a small amount of undissolved solid.
4. Filter this solution and discard the filter paper.
5. Gently heat the resulting liquid. You should get a small amount of solid.

### Observations

In the first reaction (hydrochloric acid with sodium hydroxide) the resulting solution was clear. When this solution was heated a small amount of white powder was noted. This powder is sodium chloride.

In the second reaction (sulfuric acid with copper(II) oxide) the resulting solution was blue in colour. When this solution was heated a small amount of white powder was noted. This powder is copper sulfate.

In the third reaction (hydrochloric acid with calcium carbonate) the resulting solution was clear. When this solution was heated a small amount of white powder was noted. This powder is calcium sulfate.

Try write reaction equations for the three reactions above.

### Conclusion

We used acid-base reactions to produce different salts.