Question:

The pH of boiling water is 6.4. This implies that boiling water is

Updated On: Jun 21, 2022
  • slightly basic
  • slightly acidic
  • neutral
  • amphoteric.
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The Correct Option is C

Solution and Explanation

The ph of boiling water is $6.4$. This implies that boiling water is neutral. When water is boiled, both hydrogen ion and hydroxide ion concentration increases to same extent. Hence it is neutral. With increase in the hydrogen ion concentration, pH decreases from 7 to 6.4. Also, the value of $K _{w}$ also increases as the degree of dissociation of water increases with increase in temperature.
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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