Chemistry MCQs for NEET — Practice Questions with Answers

Ka for $CH_3COOH$ at $ 25 ^\circ C $ is $ 1.754 \times 10^{–5} $ . At $ 50 ^\circ C$ , Ka is $ 1.633 \times 10^{–5} $ What will be value of $ OS^ \circ $ for the ionisation of $CH_3COOH$?

$ C_2H_6 (g) + 3.5 O_2 (g) \rightarrow 2CO_2 (g) + 3H_2O (g) $ $ \triangle S_{vap} (H_2O, l)$ = $ x_1 cal K^{–1} (boiling point + T_1) $ $ \triangle Hf (H_2O, l)$ = $ x_2$ $ \triangle Hf (CO_2)$ = $ x_3 $ $ \triangle Hf (C_2H_6) $ = $ x_4 $ Hence $ \triangle H $ for the reaction is –

$ C (s) + O_2 (g) \rightarrow CO_2, (g)$ ; OH = –94.3 kcal/mol $ CO (g) + O_2(g) \rightarrow CO_2 (g)$ ; O H = – 67.4 kcal/mol $ O_2(g) \rightarrow 2O (g)$ ; OH = 117.4 kcal/mol $ CO (g) \rightarrow C (g) + O(g)$ ; OH = 230.6 kcal/mol Calculate OH for $ C (s) \rightarrow C (g) $ in kcal/mol.

The difference between OH and OE on a molar basis for the combustion of n–octane at $ 25 ^\circ C $ would be : $ 25 ^ \circ C $

What is the work done against the atmosphere when 25 grams of water vaporizes at 373 K against a constant external pressure of 1 atm ? Assume that steam obeys perfect gas laws. Given that the molar enthalpy of vaporization is 9.72 kcal/mole, what is the change of internal energy in the above process ?

In the reaction $ CS_2 (l) + 3O_2 (g) \rightarrow CO_2 (g) + 2SO_2 (g) OH = –265 kcal $ The enthalpies of formation of $ CO_2 and SO_2 $ are both negative and are in the ratio 4 : 3. The enthalpy of formation of $ CS_2 $ is + 26 kcal/mol. Calculate the enthalpy of formation of $ SO_2 $ .

The bond dissociation energy of gaseous $H_2, Cl_2 $ and HCl are 104, 58 and 103 kcal mol– 1 respectively. The enthalpy of formation for HCl gas will be

$ AB, A_2 $ and $ B_2 $ are diatomic molecules. If the bond enthalpies of $A_2$, AB & $B_2 $ are in the ratio 1 : 1 : 0.5 and enthalpy of formation of AB from $A_2$ and $B_2$ is – 100 kJ/mol–1. What is the bond enthalpy of $A_2$ .

One mole of a gas occupying $3 dm^3 $ expands against constant external pressure of 1 atm to a volume of $ 13 dm^3 $ . The work done is –

The heat of formation of liquid methyl alcohol is kilojoule per mole using the following data will be [Heat of vaporisation of liquid methyl alcohol = 38 kJ/mol. Heat of formation of gaseous atoms from the elements in their standard states : H, 218 kJ/mol; C, 715 kJ/mol; O, 249 kJ/mol. Average bond energies : C – H, 415 kJ/mol; C – O, 356 kJ/mol O – H, 463 kJ/mol.]