8th Chapter Solved Exercise MCQs of FSC First Year Chemistry
written by Almas AnwarThe 8th chapter Solved Exercise MCQs of FSC 1st-year Chemistry offers a comprehensive collection of multiple-choice questions with answers. Each question is accompanied by a short explanation to clarify the correct choice. These solutions aim to assist students in exam preparation by simplifying complex concepts and building a strong foundation for success.
8th chapter solved MCQs with explanation
1. For which system does the equilibrium constant, K, have units of (concentration)?
(a) Nโ + 3Hโ โ 2NHโ
(b) Hโ + Iโ โ 2HI
(c) 2NOโ โ NโO
(d) 2HF โ Hโ + Fโ
Explanation: The correct answer is (c). Because the units of the equilibrium constant depend on the number of moles of reactants and products. When the number of moles of reactants equals the total number of moles of products, the equilibrium constant has no units.
2. Which statement about the following equilibrium is correct?
2SOโ (g) + Oโ (g) โ 2SOโ (g) ฮH = -188.3 kJ molโปยน
(a) The value of K falls with a rise in temperature
(b) The value of K falls with increasing pressure
(c) Adding VโOโ
catalyst increases the equilibrium yield of sulphur trioxide
(d) The value of K is equal to K
Explanation: The correct answer is (a). Because
Kp = Kc(RT)^n
^n = 2 โ (2+1) = -1
So,
Kp = Kc R-1 T-1 = Kp x 1 / T
3. The pH of 10 mol dmโปยณ of an aqueous solution of HโSOโ is:
(a) 3.0
(b) 2.7
(c) 2.0
(d) 1.5
Explanation: The correct answer is (d). Because:
- HโSOโ is a strong acid and gives 2 Hโบ ions for each molecule.
- For a 10 mol/dmยณ solution, the Hโบ concentration is 20 mol/dmยณ.
- pH = โlog [Hโบ].
- Since โlog (20) โ โ1.3 , the pH is close to 1.5.
4. The solubility product of AgCl is 2.0 ร 10โปยนโฐ molยฒ dmโปโถ. The maximum concentration of Agโบ ions in the solution is:
(a) 2.0 ร 10โปยนโฐ mol dmโปยณ
(b) 1.41 ร 10โปโต mol dmโปยณ
(c) 1.0 ร 10โปยน mol dmโปยณ
(d) 4.0 ร 10ยฒ mol dmโปยณ
Explanation: The correct answer is (b).
- What is Ksp? The solubility product (Ksp) tells us how much a substance can dissolve in water. For silver chloride (AgCl) Ksp = 2.0ร10โ10 molยฒ dmโปโถ.
- Dissolving AgCl in Water: When AgCl dissolves in water, it breaks into silver ions (Ag+) and chloride ions (Clโ): AgCl โ Ag+ + Clโ
- Setting Up the Equation: Let x be the concentration of Ag+ ions in the solution. Since each AgCl gives one Ag+ and one Clโ, the concentration of Clโ is also x.
The solubility product (Ksp) formula is:
Ksp= [Ag+] [Clโ]
So, Ksp= x ร x = x2
- Finding the Concentration of Ag+ :
We know Ksp=2.0ร10โ10.- โ Plugging this into the equation: x2= 2.0 ร 10โ10
To find x, took the square root of both sides and hereโs the answer:
x = 1.41 ร 10โ5 mol dmโ3
5. An excess of aqueous silver nitrate is added to aqueous barium chloride and the precipitate is removed by filtration. What are the main ions in the filtrate?
(a) Agโบ and NOโโป only
(b) Agโบ, Baยฒโบ, and NOโโป
(c) Baยฒโบ and NOโโป only
(d) Baยฒโบ, NOโโป, and Clโป
Explanation: The correct answer is (c). Because:
- When silver nitrate (AgNOโ) is added to barium chloride (BaClโ), silver chloride (AgCl) forms as a solid precipitate.
- This precipitate is removed by filtration.
- The filtrate contains barium ions (Baยฒโบ) and nitrate ions (NOโโป), because they are left in the solution after the reaction.
Thus, the main ions in the filtrate are Baยฒโบ and NOโโป.
