pls help me to answer science question use eng answer thx

1) pH is defined as -log[H+] so it is a measurement for the concentration of H+ (or H3O+ in real situation) in an aqueous solution. When the solution has a pH value of 7 so the concentration of H+ is 10^-7 mol per dm3. The solution is neutral. The lower the pH value (lower than 7), more acidic the solution and more concentrated of H+. The higher pH value (more than 7), the less the concentration of H+ and we called the solution is an alkali.

2) The acid/alkali indicators are compounds which show different colours with different concentration of H+. Usually one kind of indicator only changes colour in a quite narrow range so an universal indicator is a mixture of at least three compounds which gives different colours in the pH scale.

1) pH is a value indicating the basicity and acidicity of a soultion from 0 to 14, value 0 is the most acid and 14 is the most alkalis and 7 is the neutral.
to find out pH of a solution by using a equation of pH= -log[the concentration of acid]
2)Indicators will change their colour in different pH.Different indicators have their different pH value of changing their colour. But the universial indicator will show the pH with a particular pH value.