Which of the following is a physical change?

In the reaction between sodium hydroxide and tetraoxosulphate (VI) solutions, what volume of 0.5 molar sodium hydroxide would exactly neutralize 10cm\(^3\) of 1.25 molar tetraoxosulphate (vi) acid?

Sulphur exists in six forms in the solid state. This property is known as

In the reaction:
M + N → P
ΔH = +Q kJ

Which of the following would increase the concentration of the product?

A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen. If the molar mass of the compound is 180. Find the molecular formula.
[H = 1, C = 12, O = 16]