Question

The number of molecules in 4.25 g of
ammonia is


(A) 1.5 × 10²³ (B) 2.5 × 10²³

(C) 3.5 × 10²³ (D) 15 × 10²³​

Answer 1

Answer :-

Weight of ammonia = 4.25 g

17 g of ammonia contains = 6.02 × 1023 molecules.

$\Rightarrow$ Hence, number of molecules in 4.25 g of NH, = (6.02 × 1023 × 4.25) /17 = 1.50 × 1023.

Correct Option :- (A) 1.5 × 10²³

For :- @TheRyZen

Answer 2

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(A) 1.5 × 10²³

QUESTION

The number of molecules in 4.25 g of

ammonia is

OPTIONS

(A) 1.5 × 10²³

(B) 2.5 × 10²³

(C) 3.5 × 10²³

(D) 15 × 10²³

FORMULA USED

$1 \: mole = 6.023 × {10}^{23} or 6 × {10}^{23}$

$number \: of \: molecules \: in given \: weight = \frac{given \: weight}{molecular \: mass} ×1 \: mole$

WE KNOW

formula of ammonia is NH3

N stands for atomic symbol of nitrogen

H stands for atomic symbol of hydrogen

atomic mass of nitrogen(N) is 14

atomic mass of hydrogen (H) is 1

SOLUTION

step 1

calculate the molecular mass of NH3

NH3=N+H+H+H

=N+3H

molecular mass of NH3 = atomic mass of nitrogen + 3× atomic mass of hydrogen

$14 + 3 \times 1 \\ 14 + 3 \\ 17$

so atomic mass of NH3 molecule = 17u

step 2

calculate the number of molecules

number of NH3 molecules in 4.25 g of it =

$= \frac{given \: weight}{molecular \: mass} ×1 \: mole \\ \frac{4.25}{17} \times 6 \times {10}^{23} \\ 0.25 \times 6 \times {10}^{23} \\ 1.50 \times {10}^{23}$

HOPE IT HELPS