How acids and bases react · Chemistry Class 9–10 | StemPy Lab
Course 6.1·Lesson 2 of 3
How acids and bases react
Acids react with metals to give a salt and hydrogen, with carbonates and hydrogencarbonates to give a salt, water and carbon dioxide, and with bases to give a salt and water. Metal oxides are basic and non-metal oxides are acidic.
about 25 min1 simulation2 practice questions1 Python program4 questions to check yourself
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Acids with metals
An acid reacts with many metals. A salt and hydrogen gas are made.
acid+metal→salt+hydrogen
Example: zinc and dilute hydrochloric acid. Bubbles come out.
Zn+2HCl→ZnCl2+H2
Test for hydrogen. A burning candle held near the gas makes a pop sound, and the gas burns with a blue-white flame.
A base with a metal. Some metals also react with a strong base, such as sodium hydroxide: 2NaOH+Zn→Na2ZnO2+H2. Hydrogen is given out again.
Acids with carbonates and hydrogencarbonates
An acid reacts with a metal carbonate or a hydrogencarbonate to give a salt, water and carbon dioxide.
Na2CO3+2HCl→2NaCl+H2O+CO2
NaHCO3+HCl→NaCl+H2O+CO2
Test for carbon dioxide. The gas is passed through limewater, which is a solution of calcium hydroxide. The limewater turns milky.
Ca(OH)2+CO2→CaCO3+H2O
The milkiness is the white calcium carbonate. If the gas is passed for a long time, the milkiness disappears, because soluble calcium hydrogencarbonate forms: CaCO3+H2O+CO2→Ca(HCO3)2.
A flask with an acid and sodium carbonate gives bubbles of carbon dioxide gas. A bent tube leads the gas into a test tube of limewater, which turns milky.
You should find that the gas stops rising at 20mL of acid for every gram of marble.
Acids with bases: neutralisation
An acid and a base react to give a salt and water. The reaction cancels the effect of each, so it is called neutralisation.
acid+base→salt+water
NaOH+HCl→NaCl+H2O
Oxides
Metal oxides are basic. They react with acids to give a salt and water. Example: CuO+2HCl→CuCl2+H2O. The black copper oxide dissolves, and the solution turns blue-green.
Non-metal oxides are acidic. They react with bases to give a salt and water. Example: Ca(OH)2+CO2→CaCO3+H2O.
Four patterns. Acid plus metal gives salt plus hydrogen gas, such as zinc and hydrochloric acid. Acid plus metal carbonate gives salt plus water plus carbon dioxide. Acid plus base gives salt plus water, which is neutralisation. Acid plus metal oxide gives salt plus water.
Practise with new numbers
Try it in Python
This program lists the patterns and an example of each.
Remember these
Acid + metal: salt + hydrogen. Acid + carbonate: salt + water + carbon dioxide. Acid + base: salt + water.
Hydrogen burns with a pop. Carbon dioxide turns limewater milky.
Metal oxides are basic. Non-metal oxides are acidic.
Check yourself
Try each one on your own first. If you are stuck, open a hint. Then check with Show the answer.
Magnesium ribbon is dropped into dilute sulphuric acid. Name the salt and the gas.
Write, in words, the reaction of sodium hydrogencarbonate with an acid.
Is calcium oxide an acidic or a basic oxide?
What two products does every neutralisation of an acid by a base give?
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