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# Calculate the weight of $2.5\;$moles of ethane (${C_2}{H_6}$) . The molecular weight of $C = 12{\text{g/mole}}$, $H = 1{\text{g/mole}}$$75g$$25g$$30g$$60g$

Last updated date: 11th Jun 2024
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Hint: In this question, we shall calculate the molar mass of ${C_2}{H_6}$ . Then, simply use the unitary method to find the answer to this question. $6.022 \times {10^{23}}$ is Avogadro's number and represents the number of atoms/molecules present in one mole of the substance. We shall use the mole concept to find the mass of the given moles of ${C_2}{H_6}$
Formula used: ${\text{moles = }}\dfrac{{{\text{mass}}}}{{{\text{molar mass}}}}$

In the question, we are given the total number of moles. To find the total mass present we just need to multiply this value with a molar mass of ethane. Ethane contains two carbon atoms each weighing $12{\text{g/mole}}$ and six hydrogen atoms each weighing ${\text{1g/mole}}$
The molar mass of ethane = Mass of 1 mole of ethane = $2 \times 12 + 6 \times 1 = 24 + 6 = 30{\text{g}}$.
Mass of $2.5\;$moles of ethane= $2.5 \times 30 = 75{\text{g}}$.
Avogadro constant can be defined as the number of molecules, atoms, or ions in one mole of a substance: $6.022 \times {10^{23}}$ per mol. It is derived from the number of atoms of the pure isotope $^{{\text{12}}}{\text{C}}$in 12 grams of that substance and is the reciprocal of atomic mass in grams. The formulae for the mole concept can be summarized as:
${\text{No}}{\text{. of moles = }}\dfrac{{{\text{Mass of the Substance in grams}}}}{{{\text{Molar mass of a Substance}}}} = \dfrac{{{\text{Number of Atoms or Molecules}}}}{{6.022 \times {{10}^{23}}}}$.