Question

Q2. Shining a torch perpendicular on a paper makes a circular spot. If you tilt the paper, the circle is converted to an ellipse and the area of the spot increases. How much does the area increase if we tilt the paper by 23 degrees?

Answer 1

Answer:

we have to identify which one of the given reactions , a salt is reacting with a base

a) NaOH + HCl → NaCl + H₂O

b) Cu(OH)₂ + H₂SO₄ → CuSO₄ + 2H₂O

c) KOH + HCl → KCl + H₂O

d) 6NH₄OH + Al(SO₄)₃ → 2Al(OH)₃ + 3(NH₄)₂SO₄

solution : concept : general formula of a base is YOH, where Y is metal and OH is hydroxide ion.

so, NaOH , KOH and NH₄OH, Cu(OH)₂ are base.

HCl , H₂SO₄ are acid.

now let's see the reaction.

a. NaOH (base) + HCl (acid) ⇒NaCl (salt) + water

b. Cu(OH)₂ (base) + H₂SO₄ (acid) ⇒ CuSO₄ (salt) + water

c. KOH (base) + HCl (acid) ⇒ KCl (salt) + water

d. NH₄OH (base ) + Al(SO₄)₃ (salt) ⇒2Al(OH)₃ (base) + 3(NH₄)₂SO₄ (salt)

Therefore option (d) is the reaction of a salt with a base.