At what $pH$ is rain water said to be acidic?

According to the $Brønsted-Lowry$ theory, what kind of substance is a base?

Which of the following gives the correct increasing order of acidic strength?

The physiological reactions occurring in the human body take place in the range of $......\,pH.$

With the increase in the concentration of hydrogen ions,the $pH$ value will

How do metal carbonates and metal hydrogen carbonates react with acids? Give their chemical equations. Name the gas evolved during the reaction. What will happen when this gas is passed through lime water?