Question:

$50 \, mL $ of $H_2O$ is added to $50 \, mL$ of $1 \times 10^{-3}\, M$ barium hydroxide solution. What is the pH of the resulting solution?

Updated On: Mar 10, 2025
  • 3
  • 3.3
  • 11
  • 11.7
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The Correct Option is C

Solution and Explanation

In water, barium hydroxide is hydrolysed as follows,
$Ba ( OH )_{2} \rightleftharpoons Ba ^{2+}+2 OH ^{-}$
cone, of $Ba ^{2+}=1 \times 10^{-3} M$
cone. Of $\left[ OH ^{-}\right]=2 \times 1 \times 10^{-3} M$
$=2 \times 10^{-3} M$
$pOH =-\log [ OH^ -]$
$=-\log \left(2 \times 10^{-3}\right)$
$=2.69$
$p H+p O H=14$
$p H=14-p O H$
$=14-2.69$
$=11.3$
$=11.0$
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Concepts Used:

Acids and Bases

Acid is any hydrogen-containing substance that is capable of donating a proton (hydrogen ion) to another substance. Base is an ion or molecule capable of accepting a hydrogen ion from acid. 

Physical Properties of Acids and Bases

Physical PropertiesACIDSBASES
TasteSourBitter
Colour on Litmus paper Turns blue litmus redTurns red litmus blue
Ions produced on dissociationH+OH-
pH<7 (less than 7)>7 (more than 7)
Strong acidsHCl, HNO3, H2SO4NaOH, KOH
Weak AcidsCH3COOH, H3PO4, H2CO3NH4OH

Chemical Properties of Acids and Bases

Type of ReactionAcidBases
Reaction with Metals

Acid + Metal → Salt + Hydrogen gas (H2)

E.g.,

Zn(s)+ dil. H2SO4 → ZnSO(Zinc Sulphate) + H2

Base + Metal → Salt + Hydrogen gas (H2)

E.g.,

2NaOH +Zn → Na2ZnO2 (Sodium zincate) + H2

Reaction with hydrogen carbonates (bicarbonate) and carbonates

Metal carbonate/Metal hydrogen carbonate + Acid → Salt + Carbon dioxide + Water

E.g., HCl+NaOH → NaCl+ H2O

2. Na2CO3+ 2 HCl(aq) →2NaCl(aq)+ H2O(l) + CO2(g)

3. Na2CO3+ 2H2SO4(aq) →2Na2SO4(aq)+ H2O(l) + CO2(g)

4. NaHCO3+ HCl → NaCl+ H2O+ CO2

Base+ Carbonate/ bicarbonate → No reaction
Neutralisation Reaction

Base + Acid → Salt + Water

E.g., NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

Base + Acid → Salt + Water

E.g., CaO+ HCl (l) → CaCl2 (aq)+ H2O (l)

Reaction with Oxides

Metal oxide + Acid → Salt + Water

E.g., CaO+ HCl (l) → CaCl2 (aq)+ H2O (l)

Non- Metallic oxide + Base → Salt + Water

E.g., Ca(OH)2+ CO2 → CaCO3+ H2O

Dissolution in Water

Acid gives H+ ions in water.

E.g., HCl → H+ + Cl-

HCl + H2O → H3O+ + Cl–

Base gives OH- ions in water.

Read more on Acids, Bases and Salts