Q) Percentage purity of gold in 10g of chain marked 20carat (puregold=24carat)-

1)80%  2)91.6% 3)83.33% 4)96%

Q) The crystalline salt Na2SO4.xH2O on heating loses 55.9% of its weight ; the value of x in the crystalline salt is -

1)5 2)7 3)2 4)10

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Solution to second question:

The crystalline salt Na2SO4.xH2O on heating loses 55.9% of its weight ; the value of x in the crystalline salt is -

1)5 2)7 3)2 4)10

Correct option: 4

Consider 100g of Na₂SO₄.x H₂O

On heating it loses 55.90g of water.

Mole proportion Na₂SO₄ = 44.10, H₂O = 55.9

Na₂SO₄ = 44.10 = 0.3106

142

H₂O = 55.90 = 3.106

18

So let us divide by the smallest, so we have mole proportion as Na₂SO₄.H₂O = 1:10

So the salt is Na₂SO₄.10H₂O