Which of the following would be true for a 0.001 M solution of HCl?

Question

The pH is 3 and it turns litmus paper red.

The pH is 2 and it turns litmus paper red.

The pH is 2 and it turns litmus paper red.

The pH is 3 and it turns litmus paper blue.

Answer 1

HCl is a strong acid so [H+] = 0.001 M.

pH = -log [H+] = -log (0.001) = 3

Acids turn litmus paper RED.

Answer 2

The pH is 3 and it turns litmus paper red.

Answer 3

Read your notes on the Henderson-Hasselbach equation to work out the pH of the solution - then look up the colour change for litmus on google.

You seem to have made an error in the answer options as you have repeated "The pH is 2 and it turns litmus paper red" twice. I assume one of these should have litmus as blue.

Answer 4

It turns red, and I do not have a calculator, but since it is a strong acid the pH is log (to the base 10) of 0.001.