The fizz test

The idea

All metal carbonates and metal hydrogencarbonates react with acids to give the corresponding salt, carbon dioxide and water.

Fizz!

Add a spoon of baking soda (sodium hydrogencarbonate) to vinegar or lemon juice. It fizzes and gas bubbles out.

Which gas is bubbling out?

• Carbon dioxide
• Hydrogen
• Oxygen

Catch the gas

A teacher adds dilute HCl to each solid. The gas travels through the tube into lime water. Run all three tests.

Carbonate + acid → CO₂

All metal carbonates and metal hydrogencarbonates react with acids to give the corresponding salt, carbon dioxide and water.

Metal carbonate or hydrogencarbonate + Acid → Salt + Carbon dioxide + Water. Limestone, chalk and marble are different forms of calcium carbonate.

• Solid | Acid | Salt
• Na₂CO₃ | HCl | NaCl
• NaHCO₃ | HCl | NaCl
• CaCO₃ | HCl | CaCl₂

Notes

All metal carbonates and metal hydrogencarbonates react with acids to give the corresponding salt, carbon dioxide and water.

Check yourself

A gas turns lime water milky. Which gas is it?

Marble chips (calcium carbonate) are dropped in dilute HCl. What forms?

NaHCO₃ + HCl → NaCl + H₂O + ?

Which one fizzes when dilute HCl is poured on it?

• Carbon dioxide — correct. Yes! Lime water turns milky with carbon dioxide.
• Hydrogen. Hydrogen burns with a pop. It does not turn lime water milky.
• Oxygen. Oxygen does not turn lime water milky.
• Calcium chloride and hydrogen only. Hydrogen comes from metals. A carbonate gives carbon dioxide.
• Calcium chloride, carbon dioxide and water — correct. Yes! Salt + CO₂ + water.
• Calcium oxide and water. An acid and a carbonate give a salt, carbon dioxide and water.
• H₂. Hydrogen is not formed here. It is carbon dioxide.
• O₂. The gas is carbon dioxide.
• CO₂ — correct. Yes! Hydrogencarbonates also give carbon dioxide.
• A piece of chalk — correct. Yes! Chalk is calcium carbonate.
• Pure water. Water does not fizz with an acid.
• A glass bead. Glass has no carbonate to react with the acid.