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CBSE Questions for Class 11 Medical Chemistry Equilibrium Quiz 15 - MCQExams.com
CBSE
Class 11 Medical Chemistry
Equilibrium
Quiz 15
A buffer solution is $$0.25 M - CH_{3}COOH + 0.15 M - CH_{3}COONa$$, saturated in $$H_{2}S (0.1 M)$$ and has $$[Mn^{2+}] = 0.04 M$$, $$K_{a}(CH_{3}COOH) = 2.0 \times 10^{-5}$$, $$ K_{a} (H_{2}S) = 1.0 \times 10^{-21}$$
and
$$K_{sp}(MnS) = 2.5 \times 10^{-13}$$
.
Which buffer component should be increased in concentration and to which minimum value to just start precipitation of $$MnS$$?
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$$CH_{3}COOH, 1.25 M$$
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$$CH_{3}COONa, 0.25 M$$
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$$CH_{3}COONa, 1.25 M$$
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$$CH_{3}COONa, 0.50 M$$
An amount of $$0.10$$ moles of $$AgCl(s)$$ is added to one litre of water. Next, the crystals of $$NaBr$$ are added until $$75$$% of the $$AgCl$$ is converted to $$AgBr(s)$$, the less soluble silver halide. What is $$Br^{-}$$ at this point?
$$K_{sp}$$ of $$AgCl = 2 \times 10^{-10}$$ and $$K_{sp}$$ of $$AgBr = 4 \times 10^{-13}$$.
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$$0.075\ M$$
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$$0.025\ M$$
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$$1.5 \times 10^{-4}M$$
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$$0.027\ M$$
What concentration of free $$CN^{-}$$ must be maintained in a solution that is $$1.8 M - AgNO_{3}$$ and $$0.16 M NaCl$$ to prevent $$AgCl$$ from precipitating? $$K_{f}$$ for $$Ag(CN)_{2}^{-} = 6.4 \times 10^{17}$$ and $$K_{sp}$$ for $$AgCl = 1.8 \times 10^{-10}$$
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$$2.5 \times 10^{-9}M$$
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$$5 \times 10^{-5}M$$
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$$2.5 \times 10^{-5}M$$
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$$1 \times 10^{-4}M$$
When $$20 ml$$ of $$0.2 M - DCl$$ solution is mixed with $$80 ml$$ of $$0.1 M - NaOD$$ solution, $$pD$$ of the resulting solution becomes $$13.6$$. The ionic product of heavy water, $$D_{2}O$$, is
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$$10^{-15}$$
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$$10^{-16}$$
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$$4 \times 10^{-15}$$
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$$4 \times 10^{-16}$$
An amount of $$0.01$$ moles of solid $$AgCN$$ is rendered soluble in $$1 l$$ by adding just sufficient excess cyanide ion to form $$Ag(CN)^{2-}$$ and the concentration of free cyanide ion is $$2.5 \times 10^{-7} M$$. Determine $$[Ag^{+}]$$ in the solution neglecting hydrolysis of cyanide ion. $$K_{diss}$$ for $$Ag(CN)_{2}^{-} = 1.0 \times 10^{-20}$$.
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$$6.25 \times 10^{-9}M$$
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$$1.6 \times 10^{-9}M$$
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$$1.6 \times 10^{-7}M$$
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$$6.25 \times 10^{-7}M$$
A $$40.0 ml$$ solution of weak base, $$BOH$$ is titrated with $$0.1 N - HCl$$ solution. The $$pH$$ of the solution is found to be $$10.0$$ and $$9.0$$ after adding $$5.0 ml$$ and $$20.0 ml$$ of the acid, respectively. The dissociation constant of the base is ($$log 2 = 0.3$$)
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$$2 \times 10^{-5}$$
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$$1 \times 10^{-5}$$
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$$4 \times 10^{-5}$$
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$$5 \times 10^{-5}$$
Which of the following statement(s) is/are incorrect?
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When water is added to $$KCN$$, a reaction occurs because the $$CN^{-}$$ ion is a strong proton acceptor.
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No reaction occurs when $$KCl$$ is dissolved in water because neither $$K^{+}$$ nor $$Cl^{-}$$ can remove or accept proton from water.
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When water is added to sodium acetate, an acidic solution is produced because of the formation of free acetic acid from the action of water on $$CH_{3}COO^{-}$$.
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$$(NH_{4})_{2}CO_{3}$$ smells strongly of $$NH_{3}$$ because the strong base $$CO_{3}^{2-}$$ is able to remove protons from $$NH_{4}^{+}$$ ion.
Which of the following statements is/are correct?
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A buffer solution may contain a weak acid and its conjugate base.
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A buffer solution shows little change in $$pH$$ on the addition of a small amount of acid or base.
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A buffer solution can be prepared by mixing a solution of ammonium acetate and acetic acid.
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The addition of solid potassium cyanide to water increases the $$pH$$ of water.
The relation $$pK_{a} = 14 - pK_{b}$$ is true for which of the following pair(s)?
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$$MeNH_{3}^{+}, CH_{3}NH_{2}$$
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$$CH_{3}COOH, CH_{3}COO^{-}$$
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$$H_{3}O^{+}, OH^{-}$$
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$$Na^{+}, NaOH$$
If $$K_{1}$$ and $$K_{2}$$ are the first and second ionization constants of $$H_{2}CO_{3}$$ and $$K_{1} >> K_{2}$$, the incorrect relation(s) is/are
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$$[H^{+}] = [HCO_{3}^{-}]$$
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$$[H^{+}] = \sqrt{K_{1}[HCO_{3}^{-}]}$$
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$$K_{2} = [CO_{3}^{2-}]$$
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$$[H^{+}] = 2[CO_{3}^{2-}]$$
Which of the following may act as buffer in aqueous solution?
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$$NH_{4}Cl + NH_{4}OH$$
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$$CH_{3}COOH + CH_{3}COONa$$
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$$CH_{3}COONa + NaCl$$
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$$Borax + Boric acid$$
The molar ratio of dimer to monomer for $$0.1 M$$ acetic acid in benzene is equal to
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$$150 : 1$$
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$$1:150$$
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$$5:2$$
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$$2:5$$
Which of the following will occur if a $$0.1 M$$ solution of a weak acid is diluted to $$0.01 M$$ at constant temperature?
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$$[H^{+}]$$ will decrease
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$$pH$$ will increase
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Percentage ionization will increase
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$$K_{a}$$ will increase
Which of the following processes will increase $$[OH^{-}]$$ in $$NH_{4}OH$$ solution?
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Addition of $$HCl$$ solution.
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Addition of water.
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Addition of $$NH_{4}Cl$$ solution.
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Addition of solid $$NH_{4}OH$$.
A volume of $$500 ml$$ of $$0.01 M - AgNO_{3}$$ solution, $$250 ml$$ of $$0.02 M - NaCl$$ solution and $$250 ml$$ of $$0.02 M - NaBr$$ solution are mixed. The final concentration of bromide ion in the solution is ($$K_{sp}$$ of $$AgCl$$ and $$AgBr$$ are $$10^{-10}$$ and $$5 \times 10^{-13}$$, respectively.)
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$$0.01 M$$
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$$0.02 M$$
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$$0.005 M$$
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$$2.5 \times 10^{-5} M$$
In the system, $$ LaCI_3(s) + H_2O(g) + heat \rightleftharpoons LaCIO(s) + 2HCI(g) $$, equilibrium is established. More water vapour is added to distributed the equilibrium . If the pressure of water vapour at new eqilibrium is double of that at initial equilibrium, the factor by which pressure of HCI is changed is
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2 times
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$$ \sqrt { 2 } times $$
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$$ \frac { 1 }{ \sqrt { 2 } } times $$
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4 times
The amino acid alanine has two isomers, $$ \alpha $$ alanine and $$ \beta $$ alanine when equal masses of these two compound are dissolved in equal mass of a solvent, the solution of $$ \alpha $$ alanine freeze at relatively l; lower temperature, which forms $$ \alpha $$ alanine and $$ \beta $$ alanine has the larger equilibrium constant for ionization?
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$$ \alpha $$ alanine
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$$ \beta $$ alanine
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same for both
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unpredictable
Explanation
$$\alpha\space alanine$$ and $$\beta\space alanine$$ both dissociate into two ion as shown below,
$$Alanine\leftrightharpoons X^++Y^-$$
Equilibrium constant is ratio of the concentration of product and concentration of reactant.
So, $$K_{c(alanine)}=[X^+][Y^-]$$
The freezing point of the solvent decreases when a non-volatile solute is added to pure solvent this is known as depression in freezing point.
Ions in solution change the freezing point temperature.
If more ions are present in the solution, they decrease the freezing point more.
Since it's given that
$$\alpha\space alanine$$ has a lower freezing temperature it implies that
$$\alpha\space alanine$$
has more ions.
Therefore, the equilibrium constant of
$$\alpha\space alanine$$ is larger.
Hence, the correct option is (A).
The molar ratio of dimer to monomer for $$0.1 M$$ acetic acid in water (neglecting the dissociation of acetic acid in water) is equal to
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$$250:1$$
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$$1:250$$
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$$9:2500$$
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$$2500:9$$
The initial rate of hydrolysis of methyl acetate $$(1.0M)$$ by a weak acid $$(HA,1.0M)$$ is 1/100th of that of a strong acid $$(HX,1.0M)$$, at $${ 25 }^{ o }C$$. The $${K}_{a}$$ of $$HA$$ is
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$$1\times { 10 }^{ -4 }$$
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$$1\times { 10 }^{ -5 }$$
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$$1\times { 10 }^{ -6 }$$
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$$1\times { 10 }^{ -3 }$$
Single Correct Answer Type
The phenomenon in which white transparent crystal change into white is called:
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Deliquescence
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Efflorescence
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Allotropy
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Sublimation
The actual composition of nitrolim is :
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$$Ca(CN)_2$$
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$$CaC_2 +Ca (CN)_2$$
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$$CaCN_2 +C$$
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$$Ca H_2$$
Explanation
The correct option is (C).
Explanation:
When nitrogen is passed over calcium carbide at a suitable high temperature, we get a mixture called nitrolim which is a nitrogenous fertilizer, which is a mixture of calcium cyanamide and carbon.
Aqueous solution of $$HNO_3, KOH, CH_3COOH$$ and $$CH_3COONa$$ of identical concentration are provided. The pair(s) of solution which forms buffer upon mixing is (are)
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$$HNO_3$$ and $$CH_3COOH$$
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$$KOH$$ and $$CH_3COONa$$
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$$HNO_3$$ and $$CH_3COONa$$
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$$CH_3COOH$$ and $$CH_3COONa$$
Explanation
A buffer solution is an aqueous solution consisting of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid.
Of all options, only in option "D", there is a pair of a weak acid and salt of its conjugate base.
Hence, Option "D" is the correct answer.
Which one of the following salts given as acidic solution in water?
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$$CH_3COONa$$
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$$NH_4Cl$$
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$$NaCl$$
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$$CH_3COONH_4$$
Explanation
$$NH_4Cl+H_2O \rightleftarrows \underset{Weak base}{NH_4OH} +\underset{Strong\ acid}{HCl}$$.
So it is acidic in nature.
Option B is correct.
The hydrogen ion concentration of a slightly acidic water solution can be represented by
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$$10^{-pOH}$$
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$$14 - pOH$$
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$$\dfrac{K_w}{pOH}$$
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$$10^{-(14-pOH)}$$
Explanation
$$pH = - \log [H^+]$$
or, $$[H^+] = 10^{-pH}$$
$$\because pH + pOH = 14$$
$$\therefore pH = 14 - pOH$$
Thus, $$[H^+] = 10^{-(14-pOH)}$$
When $$NH_4Cl$$ is added to $$NH_4OH$$ solution, the dissociation of ammonium hydroxide is reduced. It is due to:
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Common ion effect
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Hydrolysis
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Oxidation
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Reduction
Explanation
Due to common ion effect.
This effect is known as common ion effect.
According to the reaction $$PbCl_2\rightarrow Pb^{2+} +2Cl^-$$, the solubility coefficient of $$PbCl_2$$ is:
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$$[Pb^{2+}] [Cl^-]^2$$
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$$[Pb^{2+}] [Cl^-]$$
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$$[Pb^{2+}]^2 [Cl^-]$$
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$$None\ of\ these$$
Explanation
$$PbCl_2 \rightarrow Pb^{2+} +2Cl^-$$
Solubility coefficient $$=[Pb^{2+}][Cl^-]^2$$
The concentration of $$KI$$ and $$KCl$$ in a certain solution containing both is $$0.001\ M$$ each. If $$20\ ml$$ of this solution is added to $$20\ ml$$ of a saturated solution of $$AgI$$ in the water. What will happen?
$$(K_{sp}AgCl=10^{−10};K_{sp}AgI=10^{−16})$$
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$$AgCl$$ will be precipitated
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$$AgI$$ will be precipitated
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Both $$AgCl$$ and $$AgI$$ will be precipitated
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There will be no precipitated
Explanation
Final concentration of $$I^− i.e. [I^−]=\dfrac{0.001\times 20}{40}M=0.0005M$$
$$∴ Final [Cl−]=0.0005M$$
If the solution of KCl and KI is added to a saturated solution of AgI, due to the lower $$K_{sp}$$ value of $$AgI,$$
$$ i.e. K_{sp}(AgI)$$$$=10^{−16};$$
$$ \text{AgI will be precipitated, since here }[I^-]>10−8 .$$
Ionic product of water increase if________
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Pressure is reduced
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$$H^+$$ is added
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$$OH^-$$ is added
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Temperature increases
Explanation
$$K_w$$ increases with increase temperature.
The ionic of water at $$25^oC$$ is $$10^{-14}$$. The ionic product at $$90^oC$$ will be:
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$$1\times 10^{-20}$$
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$$1\times 10^{-12}$$
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$$1\times 10^{-14}$$
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$$1\times 10^{-16}$$
Explanation
When increasing the temperature the value of ionic product also increase.
Option B is correct.
Out of the following which pair of solutions is not a buffer solution?
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$$NH_{4}Cl+NH_{4}OH$$
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$$NaCl+NaOH$$
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$$Na_{2}HPO_{4}+Na_{3}PO_{4}$$
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$$CH_{3}COOH+CH_{3}COONa$$
Explanation
Buffer solution is combination of weak acid and conjugate base. $$NaCl$$ is a salt and $$NaOH$$ is the base.
$$K_{a1},K_{a2}$$ and $$K_{a3}$$ are the respective ionisation constants for the following reactions:
$$H_{2}S\leftrightharpoons H^{+}+HS^{-}$$
$$HS^{-}\leftrightharpoons H^{+}+S^{2-}$$
$$H_{2}S\leftrightharpoons 2H^{+}+S^{2-}$$
The correct relationship between $$K_{a1},K_{a2}$$ and $$K_{a3}$$ is,
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$$K_{a3}=K_{a1}\times K_{a2}$$
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$$K_{a3}=K_{a1}+K_{a2}$$
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$$K_{a3}=K_{a1}-K_{a2}$$
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$$K_{a3}=K_{a1}/K_{a2}$$
Explanation
$$K_{a1}=\frac{[H^{+}][HS^{-}]}{[H_{2}S]}, K_{a2}=\frac{[H^{+}][S^{2-}]}{[HS^{-}]},K_{a3}=\frac{[H^{+}][S^{2-}]}{[H_{2}S]}$$,
For dibasic acid, $$K_{a3}=K_{a1}*K_{a2}$$
Which of the following salt is insoluble in water?
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$$CuSO_{4}$$
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$$CdSO_{4}$$
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$$PbSO_{4}$$
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$$Al_{2}(SO_{4})_{3}$$
Explanation
$$PbSO_{4}$$ is insoluble in water because of higher lattice energy then hydration.
Which of the following will nit function as a buffer solution
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$$NaCl$$ and $$NaOH$$
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$$NaOH$$ and $$NH_{4}OH$$
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$$CH_{3}COONH_{4}$$ and $$HCl$$
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Borax and boric acid
Explanation
A buffer solution is a salt of either weak acid and its salt with a strong base $$(AcOH+NaOAc)$$ or a weak base and its salt with a strong acid $$(NH_3+NH_4Cl).$$
$$NaCl \ and \ NaOH$$ consists of salt of strong acid and strong base.
$$NaOH \ and \ NH_4OH$$ consists of a weak base and strong base.
$$CH_3COONH_4\ and \ HCl$$ consists of strong acid and a salt.
$$\text{Borax and boric acid is an acid buffer solution. It consists of a weak acid (boric acid) and it's salt (borax) with a strong base.}$$
Compound $$(F)$$ is used as an artificial sweetner and is known as saccharin. It forms sodium salt. Which statement is correct about its sodium salt?
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$$(F)$$ has an acidic $$H$$ atom and its conjugate base is delocalised to $$(C=O)$$ group
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$$(F)$$ has an acidic $$H$$ atom and its conjugate base is delocalised to $$({SO}_{2})$$ group
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Both statements (a) and (b) are correct
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$$(F)$$ does not have an acidic $$H$$ atom
Explanation
Which of the following pairs of ions would be expected to from precipitate when their dilute solution are mixed
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$$ Na^{+},SO^{2-}_{3} $$
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$$ NH^{+}_{4},CO^{2-}_{3} $$
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$$ Na^{+}, S^{2-} $$
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$$ Fe^{2+},PO^{3-}_{4} $$
Explanation
When $$ Fe^{2+}$$ and $$PO^{3-}_{4} $$ ions combine, it forms $$Fe_3(PO_4)_2$$ that is insoluble in water.
In preparation of $$CHCl_3$$ from ethanol and bleaching powder , the latter provides
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$$Ca(OH)_2$$
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$$Cl_2$$
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Both (a) and (b)
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None of these
Explanation
$$\underset{Bleaching\ powder}{CaOCl_2} + H_2O \rightarrow Ca(OH)_2 + Cl_2$$
Option C is correct.
What will be the ionisation constant of formic acid if its 0.01 M solution is 14.5% ionised?
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$$2.1 \times 10^{-4}$$
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14.5
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0.145
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$$1.45 \times 10^{-4}$$
Explanation
$$K_a = c \alpha^{2}$$
$$\alpha = \dfrac{14.5} {100} = 0.145$$
$$K_a = 0.01 \times (0.145)^{2} = 2.1 \times 10^{-4}$$
Option A is correct.
Match the column I with column II and mark the appropriate choice.
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$$(A) \rightarrow (i), (B) \rightarrow (iii), (C) \rightarrow (ii), (D) \rightarrow (iv)$$
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$$(A) \rightarrow (ii), (B) \rightarrow (iv), (C) \rightarrow (iii), (D) \rightarrow (i)$$
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$$(A) \rightarrow (iv), (B) \rightarrow (ii), (C) \rightarrow (i), (D) \rightarrow (iii)$$
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$$(A) \rightarrow (iii), (B) \rightarrow (iv), (C) \rightarrow (ii), (D) \rightarrow (i)$$
Explanation
(A) Liquid $$\rightleftharpoons $$ Vapour
Equilibrium exists at the boiling point.
(B) Solid $$\rightleftharpoons $$ Liquid
Equilibrium exists at the melting point.
(C) Solid $$\rightleftharpoons $$ Vapour
Equilibrium exists at the sublimation point.
(D) Solute $$\rightleftharpoons $$ Solute(solution)
Equilibrium exists in a saturated solution.
The salt having the least solubility in water is :
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$$BaCl_2$$
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$$Ba(NO_3)_2$$
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$$MgSO_4$$
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$$BaSO_4$$
Explanation
The hydration enthalpy of barium sulphate is less than that of magnesium sulphate. Because of the big size of barium metal ion, the lattice enthalpy of barium sulphate increases so it is least soluble in water.
Among $$ \mathrm{FeSO}_{4} .7 \mathrm{H}_{2} \mathrm{O}(\mathrm{A}), \mathrm{CuSO}_{4} .5 \mathrm{H}_{2} \mathrm{O}(\mathrm{B}) $$$$ \mathrm{ZnSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}(\mathrm{C}), \mathrm{MnSO}_{4} \cdot 4 \mathrm{H}_{2} \mathrm{O}(\mathrm{D}), $$ isomorphous salts are
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$$ \mathrm{A} $$ and $$ \mathrm{C} $$
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$$ A $$ and $$ D $$
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$$ C $$ and $$ B $$
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$$ A $$ and $$ B $$
Explanation
In crystallography crystals are described as
isomorphous
if they are closely similar in shape.
$$FeSO_4.7H_2O(A)$$ and $$ZnSO_4⋅7H_2O(C)$$ are isomorphous.
Hence option A is correct
Mark the appropriate choice to fill up the blanks in the given paragraph.
A solution which maintains constant pH when small amounts of a acid or base are added is known as a (i) A mixture of acetic acid and sodium acetate acts as (ii) with a pH around (iii) and a mixture of ammonium chloride and ammonium hydroxide acts as (iv) with a pH around (v)
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Explanation
Acidic buffer has a pH of around 4.75 and basic buffer has a pH around 9.25.
Hence option D is correct.
Baking soda is a mixture of:
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Sodium carbonate and acetic acid
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Sodium carbonate and tartaric acid
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Sodium hydrogen carbonate and tartaric acid
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Sodium hydrogen carbonate and acetic acid
Explanation
A mixture of Sodium hydrogen carbonate and tartaric acid is
known as Baking soda.
Which solutions are mixed to form a buffer solution ?
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Strong acid and its salt with strong base
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Strong acid and its salt with weak base
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Weak acid and its salt with strong base
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Weak acid and its salt with weak base
Explanation
$$\text { Solution: Buffer solutions are of two types: } \\$$
$$\text { (1) Acidic buffer } \\$$
$$\text { (11) Basic buffer } \\$$
$$\text { Acidic buffer consists of a weak acid and its salt, } \\$$
$$\text { along with a strong base. Basic buffer is prepared } \\$$
$$\text { by mixing a weak base with its conjugate salt } \\$$
$$\text { along with a strong acid. }$$
Which of the following is not a buffer ?
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$$H_{2}CO_{3} / HCO_{3}^{-} $$
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$$CH_{3}COOH / CH_{3}COONa $$
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$$NH_{4}OH / NH_{4}Cl $$
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$$NH_{4}OH / CH_{3}COOH$$.
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