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ICSE Class 10 Chemistry Question 20 of 24

Solved 2023 Question Paper ICSE Class 10 Chemistry — Question 19

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19
Question

Question 7(iii)

Calculate:

(a) The percentage of phosphorus in the fertilizer super phosphate Ca(H2PO4)2 correct to 1 decimal point.

[At. Wt. H=1, P=31, O=16, Ca=40]

(b) Write the empirical formula of C8H18

Answer

(a) Molecular weight of Ca(H2PO4)2
= 40 + 2[2(1) + 31 + 4(16)]
= 40 + 2[2 + 31 + 64]
= 40 + 2[97]
= 40 + 194
= 234 g

234 g of Ca(H2PO4)2 contains 62 g of P

∴ 100 g of Ca(H2PO4)2 will contain = 62234\dfrac{62}{234} x 100 = 26.49% = 26.5%

Hence, 26.5% phosphorous is present in superphosphate Ca(H2PO4)2

(b) Given,

Molecular Formula = C8H18 = (C4H9)2

Molecular formula = n[Empirical formula]

∴ n = 2

Hence, Empirical formula = C4H9