Calculate the % of boron [B] in borax Na 2 B 4 O 7 .10H 2 O. [H = 1, B = 11, O = 16, Na = 23]

Chemistry

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Molecular weight of borax Na₂B₄O₇.10H₂O
= 2(23) + 4(11) + 7(16) + 10[2(1)+ 16]
= 46 + 44 + 112 + 180 = 382 g

382 g of borax contains 44 g of boron

∴ 100 g of borax will contain = $\dfrac{44}{382}$ x 100 = 11.5%

Hence, Percentage of boron is 11.5%

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