What is the $pH$ value of a basic aqueous solution?

What will be the action of the following substances on litmus paper? Dry $HCl$ gas,Moistened $NH_3$ gas,Lemon juice,Carbonated soft drink,Curd,Soap solution.

When soap is scrubbed on a stain of curry on a white cloth,why does it become reddish-brown,and why does it turn yellow again when the cloth is washed with plenty of water?

Which scientist introduced the $pH$ scale?

Which of the following formulae is correct for calculating the number of moles?

Write true or false for the following statement:
The universal indicator shows the same colour at different concentrations of hydrogen ions in a solution.