Making salts from metals and metal compounds
A solubleAble to dissolve in solvent. For example, sugar is soluble in water because it dissolves to form sugar solution. saltA compound formed by neutralisation of an acid by a base, eg a metal oxide, as the result of hydrogen ions in the acid being replaced by metal ions or other positive ions. Sodium chloride, common salt, is one such compound. can be prepared by reacting an acidCorrosive substance which has a pH lower than 7. Acidity is caused by a high concentration of hydrogen ions. with a suitable insolubleUnable to dissolve in a particular solvent. For example, sand is insoluble in water. reactantA substance that reacts together with another substance to form products during a chemical reaction. including:
- a metalShiny element that is a good conductor of electricity and heat, and which forms basic oxides.
- a carbonate
The insoluble reactant chosen depends upon the particular salt required.
As the reaction between metals and acids produces flammableAble to ignite and burn. hydrogen, chemists usually make salts by reacting a metal compound such as a metal carbonate with an acid.
Acids take part in reactions in which salts are produced. In these reactions, the salt is formed by replacing the hydrogen ionElectrically charged particle, formed when an atom or molecule gains or loses electrons. in the acids with metal ions or ammonium ions.
Learn more on salt formation in this podcast.
Listen to the full series on 大象传媒 Sounds.
Reactions with metals
A salt and hydrogen are produced when acids react with metals. In general:
acid + metal \(\rightarrow\) salt + hydrogen
For example:
hydrochloric acid + magnesium \(\rightarrow\) magnesium chloride + hydrogen
2HCl(aq) + Mg(s) \(\rightarrow\) MgCl2(aq) + H2(g)
Question
Hydrogen is collected in a test tube during the reaction between magnesium and hydrochloric acid. Describe the laboratory test for hydrogen.
Put a lighted splint near the mouth of the test tube. Hydrogen ignites with a squeaky pop.
Reactions with carbonates
A salt, water and carbon dioxide are produced when acids react with carbonates. In general:
acid + carbonate \(\rightarrow\) salt + water + carbon dioxide
For example:
hydrochloric acid + copper carbonate \(\rightarrow\) copper chloride + water + carbon dioxide
2HCl(aq) + CuCO3(s) \(\rightarrow\) CuCl2(aq) + H2O(g) + CO2(g)
Question
Carbon dioxide is given off during the reaction between copper carbonate and hydrochloric acid. Describe the laboratory test for carbon dioxide.
Bubble the gas through limewaterCalcium hydroxide solution. It turns milky in the presence of carbon dioxide.. Carbon dioxide turns limewater milky or cloudy white.