Chemistry

Solutions and pH Chemistry

451 Questions

Solutions and pH chemistry focus on the acidity or alkalinity of various substances, from human urine to acidic soils. Questions involve titration calculations, molarity determination, and understanding mole fractions. This topic is a staple in the chemistry sections of state and national level competitive exams.

Calculating solution molarityMole fraction calculationpH value interpretationAcidic soils and pHTitration and neutralization

Solutions and pH Chemistry Questions

Multiple choice salts salts and their classification acids, bases and salts chemistry

What is a titration curve?

  1. A graph of volume vs. pH for a titration.

  2. A graph of acid vs. base for a titration.

  3. A graph of acid vs. pH for a titration.

  4. A graph of volume vs. acid for a titration.

  5. A graph of base vs. pH for a titration.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A titration curve is a graph of volume of added base (or acid) vs. pH for a titration.

Multiple choice salts salts and their classification acids, bases and salts chemistry

What is titration?

  1. A technique used to analyze properties of solutions. It involves adding a titrant to the solution to be analyzed.

  2. A way to determine the concentration of an acid but not a base.

  3. A way to perform neutralization reactions.

  4. A way to determine the concentration of a base but not an acid.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Titration is a technique used to analyze properties of solutions (concentrations). It involves adding a titrant to the solution to be analyzed.
The process of adding one solution from the burette to another in the conical flask in order to complete the chemical reaction between the two solutions is known as titration. Of two solutions, one must be standard (of known concentration) and other must be of unknown strength.

Multiple choice salts salts and their classification acids, bases and salts chemistry

How do you determine the concentration of the unknown substance from the titration data?

  1. $(cH^+)(VH^+) = (cOH^-)(VOH^-)$
  2. $(cH^+)(VH^+) / (cOH^-)(VOH^-) = 1$
  3. $(cH^+)(VH^+) / (cOH^-)(VOH^-) = -log\:( pH)$
  4. $-log (cH^+)(VH^+) = pH$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

You determine the concentration of the unknown substance from the titration data by using the following equation
$\displaystyle  (cH^+)(VH^+) = (cOH^-)(VOH^-)$
$\displaystyle  (cH^+)  $  represents hydrogen ion concentration or acid concentration.
$\displaystyle   (VH^+) $ represents volume of acid solution.
$\displaystyle   (cOH^-)  $  represents hydroxide ion concentration (or base solution concentration).
$\displaystyle   (VOH^-)$  represents volume of base solution.

Multiple choice salts salts and their classification acids, bases and salts chemistry

Where does the equivalence point occur on a titration curve for a strong acid/strong base titration?

  1. At the endpoint, after pH 7.

  2. At pH 7, in the middle of the dramatic slope.

  3. At the very end of titration, between pH 10-12.

  4. Before the slope increases dramatically, between pH 2 and 4.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The equivalence point occur at pH 7, in the middle of the dramatic slope,
on a titration curve for a strong acid/strong base titration.
At the equivalence point, the salt of strong acid and strong base is completely hydrolyzed which gives a neutral solution with pH 7 as hydrogen ion concentration is equal to hydroxide ion concentration.

Multiple choice chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

1 ml ${ O } _{ 2 }$ will be equal to :

  1. $4g$ equivivalent oxygen
  2. $2g$ equivivalent oxygen
  3. $32g$ equivivalent oxygen
  4. $8g$ equivivalent oxygen
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Weight of $1$ mole of $O _2=32g$

$1g$ equivalent is the weight of substance which displaces $8g$ of $O _2$
$\therefore 32g$ of $O _2=\cfrac {32}{8}=4g$ equivalents of oxygen .

Multiple choice chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

How many grams of phosphoric acid $(H _2PO _4)$ would be needed to neutralise $100$g of magnesium hydroxide $(Mg(OH) _2)$?

  1. $66.7$ g
  2. $252$
  3. $112.6$ g
  4. $168$ g
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Apply the formula
${\left( {\dfrac{W}{Equivalent\ wt.}} \right) _{{H _3}P{O _4}}} = \left( {\dfrac{W}{Equivalent\ wt.}} \right) _{Mg{\left( {OH} \right) _2}}$
Hence,
${\dfrac{W}{{98 \times 3}} = \dfrac{{100}}{{58 \times 2}}}$
$\therefore{W = 112.6{\text{ }}gram}$
Multiple choice chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

Calculate the total volume of $0.1$ molar $KMn{O _4}$ solution that is needed to oxidized 100 mg of each furious oxalate and furious sulphate in a mixture in acidic medium. 

  1. 1.096 ml

  2. 1.32 ml

  3. 5.48 ml

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Calculate the milliequivalents of ferrous oxalate and ferrous sulphate. Since KMnO4 acts as an oxidizing agent in acidic medium, use the n-factor to determine the volume of 0.1 M solution required to neutralize the total equivalents.

Multiple choice chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

How many gram-equivalents of NaOH are required to neutralise 25 cm$^3$ of a decinormal HCl solution ?

  1. 0.00125

  2. 0.0025

  3. 0.0050

  4. 0.025
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
For acid-base reactions,
$\underset{(HCl)}{g-equivalent of acid}\, =\, \underset{(NaOH)}{g-equivalent of base}$
$\therefore$ g-equivalent of acid = $(25\,\times\, 10^{-3})dm^3\, \times\, \displaystyle \frac{1}{10}$
$=\, 25\, \times\, 10^{-4}$
$=\, 0.0025$
Multiple choice chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

How many grams of phosphoric acid would be needed to neutralize $100$ gm of magnesium hydroxide? (Molecular weight of $H _3PO _4=98$ and $Mg(OH) _2=58.3 gm$)

  1. 66.7 gm

  2. 252 gm

  3. 112 gm

  4. 168 gm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The balanced reaction is 2H3PO4 + 3Mg(OH)2 -> Mg3(PO4)2 + 6H2O. Calculate the moles of Mg(OH)2 (100/58.3), then use the stoichiometric ratio to find the required moles of H3PO4, and finally convert to grams.

Multiple choice chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

10 ml of 0.1 M solution sodium hydroxide is completely neutralised by 25 ml of 3 gram of dibasic acid in one solution the molecular weight of acid is:

  1. 225 g

  2. 250 g

  3. 300 g

  4. 150 g
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Given,
Concentration of $NaOH=0.1 N$
Volume$=10\,mL$
Mass of Dibasic acid$=3g$
Volume$=25\,mL$
Using,
$n _{1}M _{1}V _{1}=n _{2}M _{2}V _{2}$
$n _{2}=2$
$\Rightarrow 1\times 0.1\times 10=2\times25\times\cfrac{3}{M}$
$\Rightarrow M=\cfrac{2\times 25\times 3}{10\times 0.1}$
$\Rightarrow M=150\,g$
Multiple choice chemistry chemical equilibrium equilibrium in chemical processes introduction to equilibrium chemical equilibrium and acids-bases

Which of the following is true :

  1. $pk _{b}$ for $OH^{-}$ is -1.74 at $25^{o}$C
  2. The equilibrium constant for the reaction between HA ($pk _{a} = 4$) and NaOH at $25^{o}$C will be equal to $10^{10}$
  3. The pH of a solution containing 0.1 M HCOOH ($k _{a} = 1.8 \times 10^{-4}$) and 0.1 M HOCN ($k _{a} = 3.2 \times 10^{-4}$) will be nearly (3 -log 7)

  4. All of the above are correct
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice chemistry ionic equilibrium introduction to ionic equilibria in solution ionic equilibrium in solution ionisation of weak acids and weak bases

Acid strength and acid concentration represents:

  1. degree of dissociation and amount dissolved respectively

  2. amount dissolved and degree of dissociation respectively

  3. degree of dissociation and valency respectively

  4. none of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

 Acid Strength refers to the degree of dissociation ( or ionization) in an aqueous solution. The greater the number of ions dissociated, or the number of cations and anions released in solution, the stronger the acid. Thus,  hydrochloric acid  dissociates completely into $H^+$ and $Cl^-$ ions in solution, so it is very strong. Acetic acid $(CH _3COOH)$,  dissociates feebly and releases few ions in solution, so it is  a weak acid.
Acid Concentration represents the amount of acid dissolved in a solvent. It is  measured in molarity ( the number of moles of acid in 1 L of acid solution), parts per million or percentage. The concentration is a ratio of the solute to solvent content of a solution. Acidic solutions with low numbers of acidic molecules/ions in solution are called dilute solutions whereas those with high numbers of acidic molecules/ions are called concentrated solutions.

Multiple choice chemistry ionic equilibrium introduction to ionic equilibria in solution ionic equilibrium in solution ionisation of weak acids and weak bases

The dissociation constants of monobasic acids A,B,C and D are $6 \times 10^{4}, 5 \times 10^{5}, 3.6 \times 10^{6}\ and\ 7 \times 10^{10}$ respectively. The pH values of their 0.1 molar aqueous solutions are in the order:

  1. A < B < C < D

  2. A > B > C > D

  3. A = B = C = D

  4. A > B < C > D
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

As the dissociation constant increases (A<B<C<D), dissociation of acid increases (A<B<C<D) and hence $[H^+]$ increases  (A<B<C<D) and hence pH value  decreases  (A>B>C>D). 

Multiple choice chemistry ionic equilibrium introduction to ionic equilibria in solution ionic equilibrium in solution ionisation of weak acids and weak bases

The $K _a$ value for the acid $HA$ is $1.0 \times 10^{-6}$. What is the value of K for the  following reaction?
$A^+ + H _3O^+\rightleftharpoons HA + H _2O$

  1. $1.0 \times 10^{-8}$
  2. $1.0 \times 10^8$
  3. $1.0 \times 10^{-3}$
  4. $1.0 \times 10^6$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$HA + H _2O\rightleftharpoons A^+ + H _3O^+$
$K _a=\dfrac{[A^-].[H _3O^+]}{[HA]}=10^{-6}$
As the given reaction is the reverse of above reaction $K$ will the reciprocal of the above reaction.
Therefore, $K=10^6$