CSS Past Papers 2023 Chemistry Paper-I MCQs with Answers | Special Guide for CSS Aspirants

Описание: This video covers the CSS 2023 Chemistry Paper-I MCQs, providing a comprehensive solution guide tailored for CSS aspirants aiming to succeed in the Federal Public Service Commission (FPSC) exam.

1. Write the values for l, n, and m for Ψ3,1,0?
(A) 1, 3, 0 (B) 3, 1, 0 (C) 0, 3, 1 (D) None of these
Explanation:
n=3, l=1, and m =0 are the principal, azimuthal, and magnetic quantum numbers for the given wave function.
2. What is the magnetic quantum number of the orbital 2pz?
(A) 1 (B) ±1 (C) -1 (D) None of these
Explanation: For pz orbital, ml (the magnetic quantum number) is 0.
3. The weight of silver displaced by a quantity of electricity which displaces 5600ml of O2 at STP will be:
(A) 5.4g (B) 10.8g (C) 54.9g (D) None of these
Explanation: Based on Faraday's laws of electrolysis, the equivalent mass of silver displaced can be calculated, leading to the given weight.
4. On electrolysis of dilute sulphuric acid using platinum electrodes, the product obtained at the anode will be:
(A) Hydrogen (B) Oxygen (C) Hydrogen sulphide (D) None of these
Explanation: During the electrolysis of dilute H₂SO₄, oxygen gas is produced at the anode.
5. The coefficient of performance of a refrigerator is 5. If the temperature inside of said refrigerator is -20⁰ C. Calculate the temperature of the surrounding where it releases heat.
A) 11⁰ C. (B) 21⁰ C. (C) 31⁰ C. (D) None of these
Explanation: Using the formula for the coefficient of performance (COP) and thermodynamics, the temperature can be calculated as 31°C.
6. When an ideal monoatomic gas is heated at constant pressure, the fraction of heat energy that increases the internal energy of the gas is:
(A) 2/5 (B) 3/5 (C) 3/7 (D) None of these
Explanation: For a monoatomic gas, the internal energy change is proportional to the degrees of freedom, resulting in this fraction.
7. If the concentration of material X is doubled and that of Y is halved, how many times will the rate of the elementary reaction 3X + Y = X2Y change?
(A) r2= 4.5r1 (B) r2= 5r1 (C) r2= 2r1 (D) None of these
Explanation: The rate law depends on the concentrations of reactants; doubling X and halving Y results in a 4.5 times increase.
8. The chemical reaction, 2O3→ 3O2 Proceeds as O3 ⇌ O2+ [O] (fast) [O] + O3 → 2O2 (slow) The rate law expression will be:
(A) Rate = k [O] [O3] (B) Rate = k [O3]² [O2] -1 (C) Rate = k [O3]² (D) None of these
Explanation: The slow step determines the rate, which involves the concentration of O₃ squared.
9. Which one of the following is an example of adsorption?
(A) Ammonia in contact with water (B) Anhydrous CaCl2 with water (C) Silica gel in contact with water vapours (D) None of these
Explanation: Adsorption is the process where molecules adhere to the surface, and silica gel adsorbs water vapor.
10. The movement of colloidal particles towards the oppositely charged electrodes on passing electric current is known as:
(A) Tyndall effect (B) Cataphoresis (C) Brownian movement (D) None of these
11. The process of separating a crystalloid, from a colloid by filtration is called:
(A) Emulsification (B) Dialysis (C) Coagulation (D) None of these
12. Which of the following is used as a carrier gas in gas chromatography?
(A) Carbon dioxide (B) Oxygen (C) Helium (D) None of these
Explanation: Helium is commonly used as a carrier gas in gas chromatography due to its inertness and low viscosity.
13. What is Eluent?
(A) Liquid solution (B) Liquid solution that is a result from Elution (C) Solute (D) None of these
14. Which of the following HPLC detectors is used as a bulk property or general purpose detector?
(A) Electrochemical detector (B) Fluorescence detector (C) UV-Visible detector (D) None of these
15. Benzoin oxime is known as:
(A) Dioxime (B) Cupron (C) Cupric acid (D) None of these
16. In crystal field theory (CFT), the energy gap between t2g and eg sets is denoted by:
(A) 10Dq (B) 20Dq (C) 0Dq (D) None of these
17. The chemical formula of caustic potash is:
(A) NaOH (B) Ca(OH)2 (C) NH4OH (D) None of these
Explanation: The correct formula for caustic potash is KOH, which is not listed among the options.
18. Which one of the following elements shows the maximum number of different oxidation states in its compounds?
(A) Eu (B) Am (C) Cd (D) None of these
19. Gun metal is an alloy of:
(A) Cu and Al (B) Cu and Sn (C) Cu, Zn and Sn (D) None of these
20. The number of unpaired electrons in gaseous species of Mn3+, Cr3+ and V3+ respectively are:
(A) 4, 4 and 2 (B) 3, 3 and 2 (C) 4, 3 and 2 (D) None of these
Explanation: Mn³⁺ has 4 unpaired electrons, Cr³⁺ has 3, and V³⁺ has 2.

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