Question

How many moles are there in 5.3g of $KN{O_3}$?

Answer 1

The mole is defined as the measure or the basic unit for measuring the amount of substance which is present in the given sample. In 1 mole of the substance the amount present in it is equal to the amount of the substance present in the 12g of C-12 carbon atom. To calculate the number in a substance we need to divide the given mass by the molecular mass of the substance.

Complete step by step answer:
So to calculate the moles in a substance we will use the following formula. The formula is
Moles = $\dfrac{{mass}}{{molecular \; mass}}$
So the formula says that for calculating moles one should divide the mass or the given mass by the molecular mass. So now let us write the values which are given in the question itself. So the values given are:
Mass = 5.3g
Now we need to calculate the molecular mass first. So the molecular mass of $KN{O_3}$ will be:
$KN{O_3}$= 39+14+3(16)
$KN{O_3}$= 101g$mo{l^{ - 1}}$
So now we will substitute the values in the above formula. We get,
Moles = $\dfrac{{5.3}}{{101}}$
Moles = 0.052

So the number of moles present in 5.3 g of potassium nitrate is 0.052 moles.

Note: If in the question it was asked to calculate the number of molecules present in the given mass of substance then after calculating the number of moles we would have multiplied it with the Avogadro number. If in the question instead of mass volume of a substance would have given then we would have calculated the moles by dividing the given volume by 22.4L. The Avogadro number is equal to $6.023 \times {10^{23}}$