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GS
GS Set-1
Chemistry
Physical Chemistry
239

Physical Chemistry MCQ with Answers

239) Phenolphthalein gives which of the following colours in acidic medium?

Pink

Red

No colour

Violet

Answer is:

No colour

Explanation:

Colourless in acidic medium because concentration of pH is low.

Physical Chemistry MCQ with Answers

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240) If pK_{a_{of acetic acid at 25^oC is 4.75, then determine the pH of that solution in which 0.02M sodium acetate and acetic acid are present:}}

4.75

3.75

5.75

2.75

Answer is:

4.75

Explanation:

[salt] = [acid]

241) When equal volumes of the solutions are mixed, precipitation of AgCl (K_sp = 1.8 x 10⁻¹¹) will occur with:

10⁻⁴M Ag⁺ + 10⁻⁴M Cl⁻

10⁻⁵M Ag⁺ + 10⁻⁵M Cl⁻

10⁻⁶M Ag⁺ + 10⁻⁶M Cl⁻

10⁻¹⁰M Ag⁺ + 10⁻¹⁰M Cl⁻

Answer is:

10⁻⁴M Ag⁺ + 10⁻⁴M Cl⁻

Explanation:

Precipitation occurs when ionic product > solubility product.

242) pK_a values of two acids A and B are 4 and 5. The strengths of these two acids are related as:

Strength of acid A : Strength of acid B = 4 : 5

Acid A is about 3 times stronger than acid B

Acid B is 10 times stronger than acid A

The strengths of the two acids cannot be compared

Answer is:

Acid A is about 3 times stronger than acid B

243) A buffer solution has equal volumes of 0.2M NH₄OH and 0.02M NH₄Cl. The pK_b of the base is 5. The pH is:

Answer is:

10

Explanation:

pOH = pK_b + log ([salt]⁄[base])

Physical Chemistry MCQ with Answers

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239) Phenolphthalein gives which of the following colours in acidic medium?

No colour

Physical Chemistry MCQ with Answers

Related Physical Chemistry MCQ with Answers

240) If pKa of acetic acid at 25oC is 4.75, then determine the pH of that solution in which 0.02M sodium acetate and acetic acid are present:

4.75

241) When equal volumes of the solutions are mixed, precipitation of AgCl (Ksp = 1.8 x 10−11) will occur with:

10−4M Ag+ + 10−4M Cl−

242) pKa values of two acids A and B are 4 and 5. The strengths of these two acids are related as:

Acid A is about 3 times stronger than acid B

243) A buffer solution has equal volumes of 0.2M NH4OH and 0.02M NH4Cl. The pKb of the base is 5. The pH is:

10

Physical Chemistry MCQ with Answers

240) If pK_{a_{of acetic acid at 25^oC is 4.75, then determine the pH of that solution in which 0.02M sodium acetate and acetic acid are present:}}

241) When equal volumes of the solutions are mixed, precipitation of AgCl (K_sp = 1.8 x 10⁻¹¹) will occur with:

10⁻⁴M Ag⁺ + 10⁻⁴M Cl⁻

242) pK_a values of two acids A and B are 4 and 5. The strengths of these two acids are related as:

243) A buffer solution has equal volumes of 0.2M NH₄OH and 0.02M NH₄Cl. The pK_b of the base is 5. The pH is: