Which of the following is acidic and why? `SiO_2`,`Al_2O_3`, `PbO_2`, `SnO_2`.

Which of the following oxides is most acidic N_2 O_5 P_2 O_5 As_2 O_5 Sb_2 O_5

Which of the following is not present in portland cement? SiO' Al_2 O_3' CaO' Cd O'.

Which of the following are lewis acids? 'H_2 O, B F_3, H^+ , N H4+

Which of the following oxides of nitrogen is solid NO_2 N_2 O N_2 O_3 N_2 O_5

Complete the following reactions? '4Al+3O_2

Calculate the oxidation number of all the atoms in the following compounds and ions. 'CO_2, SiO_2, PbSO_4, ClO_4^-'

Which of the following is not formed when H_2S , reacts with acidic K_2Cr_2O_7 , solution?