Solved Example: 9114-01

Find out the solubility of $Ni(OH)_2$ in 0.1 M NaOH. Given that the ionic product of $Ni(OH)_2$ is $2 \times 10^{-15}$

A. $2 \times 10^{-13}$ M

B. $2 \times 10^{-8}$ M

C. $1 \times 10^{-13}$ M

D. $2 \times 10^{8}$ M

\(Ni(OH)_2{<=>} \underset{(S)}{Ni^{2+}} + \underset{(2S)}{2OH^-}\) where,
S = molar conc. of \(Ni(OH)_2\)
\(NaOH {->} Na^+ +\underset{(0.1\,M)}{OH^-}\) \[\begin{aligned} K_{SP} &= [Ni^{2+}][OH^-]^2 \\ &= (S)(2S + 0.1)^2\\ &=(S)(4S^2 + 0.01 + 0.4S) \\ &= 4S^3 + 0.01S + 0.4 S^2 \\ \end{aligned}\]

Neglecting higher power of \(S\), \[\begin{aligned} 2 \times 10^{-15} &= 0.01\ S\\ S &= 2 \times 10^{-13}M \end{aligned}\]

Correct Answer: A

• Molarity (M) is the amount of a substance in a certain volume of solution.
• Molarity is defined as the moles of a solute per liters of a solution.
• Molarity is also known as the molar concentration of a solution.

• Normality (N) is defined as the number of mole equivalents per liter of solution
• normality = number of mole equivalents/1 L of solution.

Solved Example: 9116-01

The units of normality are:

A. mole. ml$^{-1}$

B. g. equivalent. lit$^{-1}$

C. mole. Kg$^{-1}$

D. mole. lit$^{-1}$

Correct Answer: B

• Molality is a measure of the number of moles of solute in a solution corresponding to 1 kg or 1000 g of solvent.

Solved Example: 9115-01

Which of the following terms representing the concentration of a solution does not depend on temperature?

A. Molarity

B. Molality

C. Normality

D. Molar fraction

Correct Answer: B

Solved Example: 9115-02

If you are given a 10% (mass by mass) aqueous solution of sugar, what is the mass of sugar dissolved in 180 g of water? (ICAR Technician Feb 2022 Shift I)

A. 18 g

B. 1.8 g

C. 10 g

D. 20 g

Correct Answer: D

Solved Example: 9115-03

10 g substance (molar mass = 50) is dissolved in 200 ml water and density of this solution was found to be 1.05 g/ml and approx molality of the solution is: (RPSC Grade II Science 2015)

A. 1.05 mol/kg

B. 1.0 mol/kg

C. 0.1 mol/kg

D. 2.0 mol/kg

Correct Answer: B

Solved Example: 9113-01

Sulphur Dioxide when dissolved in water forms: (CTET Paper II Dec 2021)

A. Sulphur Trioxide

B. Sulphurous acid

C. Sulphuric acid

D. Sulphur

Correct Answer: B

Solved Example: 9113-02

Which of the following contains Citric acid? (RRB JE ME CBT II Aug 2019)

A. Tomato

B. Orange

C. Tamarind

D. Sour milk

Correct Answer: B

Solved Example: 9113-03

Which type of medicines are used for treating indigestion? (HP TGT (Medical) TET 2017)

A. Antibiotic

B. Analgesic

C. Antacid

D. Antiseptic

Correct Answer: C

Solved Example: 9113-04

What is the pH value of acid rain?

A. Less than 5.6

B. More than 5.6

C. Equal to 7.0

D. More than 7.0

Correct Answer: A

Solved Example: 9113-05

Which of the following substances can be used for identifying an acid solution? (BSF RO Sep 2019)

A. NaCl

B. KNO$_3$

C. Na$_2$CO$_3$

D. K$_2$SO$_4$

Correct Answer: B

Solved Example: 9118-01

Which among the following happens in an oxidation reaction?

A. Electrons are gained

B. Electrons are lost

C. Protons are gained

D. Protons are lost

A. D

B. A

C. C

D. B

Correct Answer: D

Solved Example: 9118-02

Which one of the following statements is NOT correct for the given reaction?

A. Iron is the reducing agent

B. The solution turns green in colour after the reaction

C. Copper is a more reactive metal than iron

D. The reaction is an example of a redox reaction

Correct Answer: C

Solved Example: 9120-01

Valency of an element depends on which of the following?

I. Number of losing electron

II. Number of gaining electron

III. Number of sharing electron

A. Only I and II

B. Only I and III

C. Only II and III

D. All I, II and III

Correct Answer: D

Solved Example: 9120-02

The oxidation state of V in V_2(O^{-4})_7 is: (MPSC Rajyaseva Prelims Aug 2022 GS Paper-I)

A. +5

B. -5

C. +4

D. +10

Correct Answer: A

The solubility of a substance is the amount of that substance that will dissolve in a given amount of solvent. Factors that affect solubility:

• Temperature: Solubility generally increases with temperature.
• Common ion effect: Common ion reduces solubility.
• pH of solution: pH affects the solubility of ionic compounds
• Formation of complex ion: The formation of complex ion increases solubility.

Solved Example: 9119-01

The solubility product for the dissociation of Mg(OH)$_2$ is 8 $\times$ 10$^{-9}$. Determine the concentration of OH$^-$ at equilibrium expressed as milligram per litres of CaCO$_3$. (JKSSB JE CE Shift III Oct 2021)

A. 252 mg/l

B. 50 mg/l

C. 300 mg/l

D. 126 mg/l

Correct Answer: D

Solved Example: 9119-02

A solution in which no more solute can be dissolved at a given temperature is called: (MP Vyapam AAO Aug 2018 Shift II)

A. Unsaturated solution

B. Universal solvent

C. Volatile solution

D. Saturated solution

Correct Answer: D

Definition:

pH is a measure of concentration of [H\(^+\)].

The pH Scale:

\[pH = -\log_{10}{H^+}\]

• Pure water has a pH of 7.

• Acidic solutions have pH less than 7.

• Base solutions have pH more than 7.

The pOH Scale:

\[pH + pOH = 14\] \[pOH = 14- pH\]

Solved Example: 9121-01

The pH value of the solution in which particular amino acid does not migrate under the influence of an electric field is called its: (MP Forest Guard Jul 2017 Shift I)

A. Effusion point

B. Neutralisation point

C. Isoelectric point

D. Eutectic point

Correct Answer: C

Solved Example: 9121-02

The solution which resist the change in pH is called _____ Solution. (PGCIL DT Elec Aug 2021 NR III)

A. Acidic

B. Basic

C. Buffer

D. Neutral

Correct Answer: C

Solved Example: 9121-03

Which of the following statements are correct about an aqueous solution of an acid and a base?

1. Higher the pH, stronger is the acid.
2. Higher the pH, weaker is the acid.
3. Lower the pH, stronger is the base.
4. Lower the pH, weaker is the base.

A. 1 and 3

B. 2 and 3

C. 1 and 4

D. 2 and 4

Correct Answer: D

Solved Example: 9121-04

The pH of water at 25$^\circ C$ is 7. When it is heated to 100$^\circ C$, the pH of water: (SSC MTS Oct 2021 Shift I)

A. Increases

B. Decreases

C. Remains same

D. Decreases up to 27$^\circ C$ and then increases

Correct Answer: B

Solved Example: 9121-05

What will happen when a few drops of HCl are added to a solution having a pH of 6.5? (ICAR Tech Mar 2022 Shift II)

A. The solution will become more acidic and the pH will decrease

B. The solution will become more acidic and the pH will increase

C. The solution will become less acidic and the pH will increase

D. The solution will become more alkaline and the pH value will increase

Correct Answer: A

Solved Example: 9122-01

Which of the following indicates that the pK of an acid is numerically equal to the pH of the solution when the molar concentration of the acid and its conjugate base are equal?

A. Michaelis-Menten equation

B. Haldanes equation

C. Henderson-Hasselbalch equation

D. Hardy-Windberg law

Correct Answer: C

Solved Example: 9117-01

In which group of the modern periodic table are halogens placed? (RRC Group D Paper II Sep 2018 Shift I)

A. 16th

B. 18th

C. 1st

D. 17th

Correct Answer: D

Solved Example: 9117-02

Elements of Second period are known as: (UP TGT Science 2016)

A. Typical element

B. Bridge element

C. Transitional element

D. Normal element

Correct Answer: B

Solved Example: 9117-03

What number of elements are provided in the modern periodic table? (DSSSB PGT Sociology Jun 2021 Shift I)

A. 108

B. 100

C. 94

D. 118

Correct Answer: D

Solved Example: 9117-04

The most electropositive halogen is: (UP TGT Science 2019)

A. F

B. CI

C. Br

D. I

Correct Answer: D

Solved Example: 9117-05

Modern periodic law was given by: (UP TGT Science 2016)

A. Dalton

B. Mendeleev

C. Dobereiner

D. Mosley

Correct Answer: D