Acids and bases Flashcards
What is a pH scale?
Is a measure of how acidic or alkaline a solution is.
What is the relationship between the pH scale and acidity and alkaline
- The lower the pH solution, the more acidic it is.
- The higher the pH solution the more alkaline it is.
- A neutral substance has a pH of 7
How can we measure a pH solution?
- An indicator: a dye that changes color according to its pH level.
- pH probe attached to a pH meter: can be used to measure pH electronically.
What is an acid?
- An acid is a substance that forms aqeuous solutions with a pH less than 7.
- Acids form H+ ions in water.
What is a base?
- A substance with a pH greater than 7.
- An alkali is a base that dissolves in water to form a solution with a pH greater than 7.
- Alkalis form OH- ions in water.
What is the reaction between acids and bases called?
Neutralisation
What is the formula for neutralisation?
acid + base —–> salt + water
What is the neutralisation in terms of H+ and OH- ions?
H+(aq) + OH-(aq) —–> H2O(1)
What are titrations?
Titrations allow you to find out how much exactly needed to neutralise a quantity of alkali.
This data can be used to find out the concentration of the acid or alkali.
How do we do the titration method?
1) To find the concentration of some alkali use a pipette and a pipette filter, add a set volume to a conical flask. Add two or three drops of indicator too.
2) Use a funnel to fill a burette with some acid of know concentration. Record the initial volume of the acid in the burette.
3) Using burette add the acid to the alkali a bit at a time while giving the conical flask a swirl. Go especially slowly when you think the end point is about to be reached.
4) The indicator changes color when all the alkali has been neutralised.
5) Record the final volume of acid in the burette, and use it along with the initial reading to calculate the volume of acid used to neutralise the alkali.
