Find the temperature from following graph so that highest amount of a gas is adsorbed

Which of the following is existing oxoacid of fluorine?

Which of the following compounds is formed when ether is dissolved in cold concentrated sulphuric acid?

Calculate the work done in joule if 1 mole of ideal gas is compressed from $25 \mathrm{dm}^3$ to $13 \mathrm{dm}^3$ at constant external pressure 4 bar.