Question

If a $360mL$ sample of helium contains $0.25$ moles, how many molecules of chlorine gas would occupy the same volume at the same pressure and temperature?

• A. $1.2\times {10}^{24}$
• B. $6.022\times {10}^{23}$
• C. $3.01\times {10}^{23}$
• D. $1.51\times {10}^{23}$
• E. $7.55\times {10}^{22}$

Answer 1

Answer: (D)

$1.51\times {10}^{23}$

For equal volumes of two gases at similar conditions of temperature and pressure, the number of moles of two gases will be same.
Hence, the number of moles of chlorine are 0.25.
When the number of moles of multiplied with Avogadro's number, the number of molecules are obtained.
Hence, the number of molecules of chlorine gas $=0.25$ mol $\times 6.02\times {10}^{23}$ molecules/mol $=1.51\times {10}^{23}$ molecules.