Solved Sample Paper 3 — Question 8

1. True
   Reason — Weak acids are partially dissociated in fused or aqueous solution hence allow small amount of electricity to flow through them and thus, have low electrical conductivity.
2. False
   Reason — Acids with a higher concentration of H⁺ (aq) ions are strong acids and acids with a lower concentration of H⁺ (aq) ions are weak acids.

(b) Molecular weight of Na₂B₄O₇.10H₂O
= 2(23) + 4(11) + 7(16) + 20(1) + 10(16)
= 46 + 44 + 112 + 20 + 160
= 382 g

382 g of Na₂B₄O₇.10H₂O contains 46 g of Na

∴ 100 g of Na₂B₄O₇.10H₂O will contain = $\dfrac{46}{382}$ x 100 = 12.04%

Hence, 12.04% of sodium is present in Na₂B₄O₇.10H₂O