Vardaan Learning Institute

Ans: (b) Baking soda
Baking soda is $NaHCO_3$, which does not have water of crystallisation.

Ans: (d) weak acid and strong base
It is formed from Carbonic acid ($H_2CO_3$, weak) and Sodium Hydroxide ($NaOH$, strong).

Ans: (a) Basic
It is a salt of Phosphoric acid (weak) and Calcium Hydroxide (strong base), so it is basic.

Ans: (d) 10
A base turns red litmus blue. Bases have pH > 7.

Ans: (d) (ii) and (iv)
(ii) Higher pH means lower $H^+$ conc, so weaker acid.
(iv) Lower pH means less basic (closer to 7 or acidic). Strong bases have pH near 14.

Ans: (b) HCl
Egg shells contain Calcium Carbonate ($CaCO_3$) which reacts with acid ($HCl$) to release $CO_2$ gas which turns lime water milky.

Ans: (c) Antacid
Antacids (bases) neutralize excess acid in the stomach causing indigestion.

Ans: (b) Bluish-green
Formation of Copper(II) Chloride ($CuCl_2$) makes solution bluish-green.

Ans: (c) Strong base
NaOH dissociates completely in water to give $OH^-$ ions.

Ans: (d) Hydrochloric acid
The solution is basic (Red to Blue). To reverse it (Blue to Red), an acid ($HCl$) must be added to neutralize and make it acidic.

Ans: (a) Both A and R are true and R is the correct explanation of A.
$NH_4Cl$ is a salt of Strong Acid ($HCl$) and Weak Base ($NH_4OH$). Such salts are acidic with pH < 7.

Ans: (d) A is false but R is true.
Antacids are used to relieve indigestion (Correct), but they contain mild BASES (not weak acids) to neutralize acid.

Ans: (d) A is false but R is true.
Dry $HCl$ gas does NOT change the colour of dry litmus paper because ionization does not occur without water.

Ans: (a) Both A and R are true and R is the correct explanation of A.
Moisture causes PoP to set into hard Gypsum, making it unusable.

(i) Calcium oxychloride, $CaOCl_2$.
(ii) It gives off chlorine gas because it reacts with carbon dioxide in the air to release chlorine.
(iii) Used for bleaching cotton and linen in textile industry.

Fixed number of water molecules present in one formula unit of a salt.
(i) Green vitriol ($FeSO_4 \cdot 7H_2O$): 7
(ii) Washing soda ($Na_2CO_3 \cdot 10H_2O$): 10
(iii) Plaster of Paris ($CaSO_4 \cdot \frac{1}{2}H_2O$): 0.5 (Half).

(i) Solution A (pH = 0) has highest $H^+$ concentration (Lower pH = Higher Acidity).
(ii) Hydrochloric acid ($HCl$). Excess acid causes pain and irritation (Acidity). Cured by taking antacids like Magnesium hydroxide (Milk of Magnesia).

Student needs to draw the labelled diagram of electrolysis of water/acid solution showing anode, cathode, battery, and gas collection.

(a) Acid dissociates into ions ($H^+$) in water which carry current.
(b) Sour substances consist of acids which react with brass (alloy of Cu and Zn) to form poisonous salts.
(c) Tap water contains ions/salts which conduct electricity; distilled water is pure and has no free ions.

Salts having the same positive or negative radicals belong to a family.
(i) Sulphate family / Potassium family
(ii) Sulphate family / Sodium family
(iii) Chloride family / Sodium family
(iv) Chloride family / Ammonium family

(i) Soil B (pH 4.5) is acidic. Powdered chalk ($CaCO_3$) is basic, so it neutralizes the acidity.
(ii) Acid rain lowers river water pH. If pH drops below 5.6, aquatic life cannot survive.
(iii) Formula: $CaSO_4 \cdot \frac{1}{2}H_2O$.
Prep: $CaSO_4 \cdot 2H_2O \xrightarrow{373K} CaSO_4 \cdot \frac{1}{2}H_2O + 1\frac{1}{2}H_2O$.
Storage: It absorbs moisture to form hard solid Gypsum ($CaSO_4 \cdot 2H_2O$), becoming useless.

(i) Sodium carbonate decahydrate, $Na_2CO_3 \cdot 10H_2O$.
Solvay Process:
1. $NaCl + NH_3 + H_2O + CO_2 \rightarrow NaHCO_3 + NH_4Cl$
2. $2NaHCO_3 \xrightarrow{\Delta} Na_2CO_3 + H_2O + CO_2$
3. $Na_2CO_3 + 10H_2O \rightarrow Na_2CO_3 \cdot 10H_2O$.
(ii) Uses: Remove permanent hardness of water; Manufacture of glass/soap.

(i) Neutral (NaCl is a neutral salt).
(ii) Green (Neutral pH = 7).
(iii) Acid rain is caused by oxides of sulphur and nitrogen dissolving in rain water to form acids ($H_2SO_4$, $HNO_3$), lowering pH below 5.6.

(i) Chlor-alkali process.
(ii) $NaHCO_3$.
(iii) $Ca(OH)_2 + Cl_2 \rightarrow CaOCl_2 + H_2O$.