Calculate the percentage of Boron ( $B$ ) in $N a_{2} B_{4} O_{7} .10 H_{2} O$ . Answer correct to 1 decimal place. [H = 1, B = 11, O = 16, Na = 23].

12.5 %

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10.2 %

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11.1 %

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11.5 %

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Solution

The correct option is D
11.5 %

Relative molecular mass of $N a_{2} B_{4} O_{7} .10 H_{2} O$ = 23 $\times$ 2 + 11 $\times$ 4 + 16 $\times$ 7 + 10(2 $\times$ 1 + 16) = 46 + 44 + 112 + 180 = 382 g.

$∴$ Amount of Boron ( $B$ ) in $N a_{2} B_{4} O_{7} .10 H_{2} O$ = 44 g.

$∴$ Percentage of Boron = $\frac{44 \times 100}{382}$ = 11.5%

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Similar questions

Find the percentage of
(a) oxygen in magnesium nitrate crystals $[M g (N O_{3})_{2} 6 H_{2} O]$ .
(b) boron in $N a_{2} B_{4} O_{7} . 10 H_{2} O . [H = 1, B = 11, O = 16, N a = 23] .$
(c) phosphorus in the fertilizer superphosphate $C a (H_{2} P O_{4})_{2}$

(a) Calculate the percentage of boron (B) in borax (Na₂B₄O₇·10H₂O). (H = 1, B = 11, O = 16, Na = 23).
(b) (i) The compound A has the following percentage composition by mass:
Carbon = 26.7%, oxygen = 71.1%, hydrogen = 2.2%. Determine the empirical formula of A (H = 1, C = 12, O = 16)
(ii) If the relative molecular mass of A is 90, what is the molecular formula of A?

Q. The % of boron in borax (

N a_{2} B_{4} O_{7} .10 H_{2} O

) is :

[

H = 1, B = 11, O = 16, N a = 23

]

Calculate the percentage of phosphorus in the fertilizer, superphosphate $C a (H_{2} P O_{4})_{2}$ .(Correct to 1 decimal point). [H = 1, O = 16, P = 31, C = 40]

Q. Calculate the percentage by weight of: (a)

C

C O_{2}

, (b)

N a

N a C O_{3}

, (c)

A l

in aluminium nitride.

[

C = 12, O = 16, H = 1, N a = 23, A l = 27, N = 14

]

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Calculate the percentage of Boron (B) in Na2B4O7.10H2O. Answer correct to 1 decimal place. [H = 1, B = 11, O = 16, Na = 23].

The correct option is D 11.5 % Relative molecular mass of Na2B4O7.10H2O = 23 × 2 + 11 × 4 + 16 × 7 + 10(2 × 1 + 16) = 46 + 44 + 112 + 180 = 382 g. ∴ Amount of Boron (B) in Na2B4O7.10H2O = 44 g. ∴ Percentage of Boron = 44×100382 = 11.5%

Calculate the percentage of Boron ( $B$ ) in $N a_{2} B_{4} O_{7} .10 H_{2} O$ . Answer correct to 1 decimal place. [H = 1, B = 11, O = 16, Na = 23].