Answer/ Explanation: To calculate the number of molecules of methane (CH4) in 125 g of CH4, we need to use the molar mass of CH4 and Avogadro's number.
1. Determine the molar mass of CH4:
The molar mass of CH4 is calculated by summing the atomic masses of all its constituent atoms:
Molar mass of C = 12.01 g/mol
Molar mass of H = 1.008 g/mol
Therefore, the molar mass of CH4 is:
Molar mass of CH4 = (4 * Molar mass of H) + Molar mass of C
Molar mass of CH4 = (4 * 1.008 g/mol) + 12.01 g/mol
Molar mass of CH4 = 16.04 g/mol
2. Calculate the number of moles of CH4:
Using the given mass of 125 g and the molar mass of CH4, we can calculate the number of moles of CH4 using the formula:
Number of moles = Mass / Molar mass
Number of moles of CH4 = 125 g / 16.04 g/mol
Number of moles of CH4 ≈ 7.79 mol
3. Convert moles to molecules:
To convert moles to molecules, we use Avogadro's number, which is approximately 6.022 x 10^23 molecules per mole.
Number of molecules = Number of moles * Avogadro's number
Number of molecules of CH4 = 7.79 mol * 6.022 x 10^23 molecules/mol
Number of molecules of CH4 ≈ 4.69 x 10^24 molecules
Therefore, there are approximately 4.69 x 10^24 molecules of methane (CH4) in 125 g of CH4.