AIIMS AIPMT PMT – Physical Chemistry Assertion Reason Questions

1. Assertion : The volume of a gas is directly proportional to the number of moles of the gas.
Reason : The ratio of the volumes of the reactants to products are in agreement with their molar ratio.
2. Assertion : The decomposition of NH3 on finely divided platinum surface is first order when the concentration is low, however at higher concentration, the reaction becomes zero order.
Reason : In first order reaction, the rate of reaction is proportional to the first power of the concentration of the reactant.
3. Assertion : In the reaction, SO2Cl2(g) = SO2(g) + Cl2(g), the reaction shifts to backward direction on increasing pressure.
Reason: The increase in pressure at equilibrium shifts the reaction towards lesser number of moles.
4. Assertion: Zinc blende and wurtzite both have fee arrangement of sulphide ions.
Reason : There are four formula units of ZnS in both.
5. Assertion: Enthalpy changes are positive when Na2S04 .10H20, CuS04 .5H20 and salt like NaCl, KCl etc. (which do not form hydrates) are dissolved in water. But enthalpy changes are negative when anhydrous salts capable of forming hydrates are dissolved in water.

Reason : The difference in the behaviour is due to large difference in the molecular weights of hydrated and anhydrous salts. The substance with larger molecular weight usually shows positive enthalpy changes on dissolution.
6. Assertion : SeCl4 does not have a tetrahedral structure.
Reason : Se in SeCl4 has two lone pairs of electron.
7. Assertion : Equivalent weight of KMnO4 in acidic medium is M/5 (M = mol. wt.) while in basic medium, it is equal to M/3.
Reason : In acidic medium, 1 mol of MnO4 gains 5 electrons while in basic medium it gains 3 electrons.
8. Assertion : Galvanic cells containing hydrogen, methane, methanol etc. as fuels are called fuel cells.

Reason : They are designed to convert the energy of combustion of fuels directly into electrical energy.
9. Assertion : BF3 is a weaker Lewis acid than BCl3.
Reason : The planar BF3 molecule is stabilized to a greater extent than BCl3 by B – X π -bonding.

10. Assertion : ln Sommerfeld model, circular orbit is possible for the electron in K-shell.
Reason : Electron present in K-shell corresponds to principal quantum number n = 1.

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