Question

Find the molecular mass (in kilogram) of an ammonia molecule $ N{H_3} $ .

Answer 1

Hint: The importance of the molecular mass is defined by the number of molecules which present in the given moles of the compound. The molecular mass can be calculated using the atomic mass of each of the molecules and the number of molecules involved.

Complete step by step answer
The molecular mass of any specific molecule can be defined according to the different atoms which are involved in the formation of the given molecule. For the formation of $ N{H_3} $ requires one atom of $ N $ and three atoms of $ H $ . Therefore, the atomic mass for each of the elements can be calculated. At first, the atomic mass for $ N $ is $ 14g/mol $ and there is only one $ N $ which is why from there the mass for $ N $ is $ 14g/mol $ . The atomic mass for $ H $ is $ 1g/mol $ and there are three hydrogen atoms involved which form the atomic mass of all $ H $ is $ 3g/mol $ .
Therefore, the molecular mass of the $ N{H_3} $ molecule is formed with the mass of all the atoms involved in the formation of the given molecule. Hence the two atomic masses calculated for $ N $ residue and that of the $ H $ residue will be:
 $ N{H_3} = (3 + 14) = 17g/mol $
The number of molecules which are present in one mole of $ N{H_3} $ is $ 6.022 \times {10^{23}} $ . For one molecule of ammonia, the mass would be = $ \dfrac{{17}}{{6.022 \times {{10}^{23}}}}g $ .
Therefore, for each of the molecules the mass will be $ 2.823 \times {10^{ - 23}}g $ or $ 2.823 \times {10^{ - 26}}kg $ .
The calculation of the molecular mass in kilograms is calculated using the factor of $ 1000 $ from the previous mass and the $ N{H_3} $ molecule has the mass $ 2.823 \times {10^{ - 26}}kg $ .

Note
The $ N{H_3} $ molecular mass is at first calculated for one mole and from there the calculation for a single molecule can be done. The kilograms of each of the molecules need to be calculated changing the units for the measurement. But at first, for a specific mole, the number of molecules need to be calculated.