Please can I have help on (I) as I’m so stuck and confused

Phosphorous acid, h3po3(aq) , is a diprotic oxyacid that is an important compound in industry and agriculture. the values of phosphorous acid are 1.30 6.70 calculate the ph for each of the given points in the titration of 50.0 ml of 1.5 m h3po3(aq) with 1.5 m koh(aq) .

A50.0 ml sample of gas at 20.0 atm of pressure is compressed to 40.0 atm of pressure at constant temperature. what is the new volume? 0.0100 ml 0.325 ml 25.0 ml 100. ml

Air can be considered a mixture. which statement does not explain why?