Question

The number of molecules in 4.2 gram of amonia is aprox

Answer 1

Answer:

Molar mass of ammonia is 17g . So 17g ammonia contains 6.022×10^23 number of ammonia molecules. So 4.25 g ammonia will contain (6.022×10^23×4.25)/17 = 1.5×10^23 number of ammonia molecules. Each molecule contain 4 atoms (1 N atom and 3 H atoms

Answer 2

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$number \: of \: moles = \frac{given \: mass}{molar \: mass}$given mass of amonia(NH3)=4.2 gram

molar mass of amonia =atomic mass of nitrogen +atomic mass of hydrogen x3

molar mass =14+6=20u

then

$no. \: of \: moles = \frac{4.2g}{20u}$

$no. of \: moles = 0.21mol$