What type of reaction occurs when an acid reacts with an alkali?
Neutralisation reaction
What is a base?
-A substance that neutralises an acid
What is an alkali?
A substance that neutralises an acid.
A base that is soluble (dissolves) in water.
Give 2 examples of bases.
Copper oxide (CuO) Calcium oxide (CaO)
Give an example of an alkali.
Sodium Hydroxide (NaOH)
If an acid is added to an alkali does the pH increase or decrease?
Decrease
If an alkali is added to an acid does the pH increase or decrease?
Increase
A farmer wants to start growing sweetcorn on his farm. He has found out that sweetcorn grows best in soil with a pH value of 7.5. Explain how he can use knowledge of acids, alkalis, and neutralisation to find out the pH value of his soil to make sure he gets the best crop possible.
- Use an indicator to determine the pH value of the soil.
- Add acid to reduce the pH value if it is alkaline.
- Add alkali to increase the pH value if it is too acidic.
- Adding acid/alkali causes a neutralisation reaction and changes the pH value.
- The pH value will change over time due to weather/leeching into the surrounding soil/plant or animal waste.
- The pH value will need to be regularly monitored and adjusted.
Suggest how environmental organisations could calculate the amount of alkali needed to raise the pH of an acidic lake.
- Measure pH of lake water.
- Select a suitable alkali that can be used to neutralise the pH.
- Carry out an investigation to find out the exact volume of alkali needed to neutralise the sample volume.
- Carry out a suitable number of repeats including from various locations to obtain an average pH/amount of alkali needed.
Acid + Alkali –>
Salt + Water
