Final answer:
To find the number of molecules of ethane in 0.700 g, calculate the number of moles using the molar mass of ethane and then multiply by Avogadro's number. The calculation yields approximately 1.40 × 1022 molecules.
Step-by-step explanation:
The question asks how many molecules of ethane (C2H6) are present in 0.700 g of C2H6. To find the number of molecules, we first need to calculate the number of moles of ethane in 0.700 g and then use Avogadro's number to convert moles to molecules.
Step 1: Calculate the molar mass of ethane (C2H6).
- Molar mass of carbon (C) = 12.01 g/mol
- Molar mass of hydrogen (H) = 1.01 g/mol
- Molar mass of C2H6 = (2 × 12.01 g/mol) + (6 × 1.01 g/mol) = 24.02 g/mol + 6.06 g/mol = 30.07 g/mol
Step 2: Calculate the number of moles of ethane.
moles of C2H6 = mass of C2H6 / molar mass of C2H6
= 0.700 g / 30.07 g/mol
= 0.02328 moles of C2H6
Step 3: Use Avogadro's number to find the number of molecules.
Avogadro's number = 6.022 × 1023 molecules/mol
Number of molecules = moles of C2H6 × Avogadro's number
= 0.02328 moles × 6.022 × 1023 molecules/mol
= 1.40 × 1022 molecules of C2H6