pH scale and indicators
Cards (18)
- When an acid is dissolved in water we get an acidic solution.
- When a base dissolves in water it is an alkali and makes a alkaline solution.
- What is a base?A substance that reacts with an acid to neutralise it and produce salt.
- Pure water is neutral (pH is 7) and so is paraffin.
- If a universal indicator is added to a solution it changes colour that shows the pH of the solution.
- When acids dissolve in water they produce hydrogen ions, H+. These are sometimes called protons.
- Acids are often produced from non-metal oxides
- When alkalis dissolve in water they produce hydroxide ions, OH-
- A base is chemically opposite to an acid. Some bases dissolve in water and are called alkalis. Other bases, including metal oxides, do not dissolve in water.
- Neutralisation reactions involve the loss and gain of hydrogen ions, this process is sometimes referred to as proton transfer.
- A dilute acid has the acid molecules mixed with a large amount of water, so that there is only a low concentration of H+ ions.
- Concentrated acids have little to no water molecules mixed with the acid molecules, meaning the concentration of H+ ions is high.
- The pH scale measures from 0 - 14
- Neutralisation of dilute acidsAcid + alkali --> salt + waterAcid + base --> salt + waterAcid + metal carbonate --> salt + water + carbon dioxide
- Naming saltsHydrochloric acid produces chloridesNitric acid produces nitratesSulfuric acid produces sulfate
- Chemical test - Test for carbon dioxide gasBubble gas through the lime water (calcium hydroxide solution) and it will turn milky (cloudy) if carbon dioxide is present.
- Chemical test - Test for carbonates
- Carbonates react with dilute acids to create carbon dioxide
- This gas can be bubbled through lime water; if the lime water goes cloudy, the gas is CO2
- Chemical test - Test for sulfate ions
- First add dilute hydrochloric acid, followed by barium chloride solution
- A white precipitate will form if sulphate ions are in this solution