Acids and Bases

Question 1

What is the pH scale?

Answer 1

The pH scale is a measure of how acidic or alkaline a solution is. The lower the pH the more acidic it is, the higher the pH the more alkaline it is.

Question 2

What would the pH of a neutral solution be?

Answer 2

pH 7

Question 3

How can you measure the pH of a solution?

Answer 3

1) by using universal indicator - a dye that changes colour depending on whether a solution is more acidic, neutral and alkali using the pH scale. A more red/orange colour would be more acidic, a green would mean neutral and a purple would mean alkali
2)A pH probe attached to a pH meter- this can be used to measure pH electronically. The probe is placed in the solution and the pH is given on digital display making it more accurate that an indicator.

Question 4

what is an acid?

Answer 4

an acid is a substance that forms aqueous solutions with a pH less than 7. Acids form positive hydrogen ions in water (H+ ions)

Question 5

What are bases?

Answer 5

Chemicals that neutralise acids and produce salt and water. Bases have a pH greater than 7

Question 6

what is an alkali?

Answer 6

An alkali is a base that is soluble in water. Alkalis form negative hydroxide ions in water (-OH ions)

Question 7

What is the reaction for neutralisation?

Answer 7

acid + base —> salt + water
or
H+(aq) + OH-(aq) —> H2O(I)

e.g.NaOH(aq)+HCL(aq)—>NaCl(aq)+H2O

Question 8

What happens when an acid and a base react?

Answer 8

They neutralise eachother