How many H atoms are present in 7.2g of propane, C3H8?
To determine the number of H atoms present in 7.2g of propane (C3H8), we need to use the molar mass and stoichiometry.
1. Start by finding the molar mass of propane (C3H8). The molar mass is the sum of the atomic masses of the elements in a compound.
The atomic mass of carbon (C) is approximately 12.01 grams/mol, and the atomic mass of hydrogen (H) is approximately 1.01 grams/mol.
Molar mass of propane (C3H8) = (3 * molar mass of C) + (8 * molar mass of H)
= (3 * 12.01) + (8 * 1.01)
= 36.03 + 8.08
= 44.11 grams/mol
2. Convert the given mass of 7.2g into moles by using the formula:
Number of moles = Mass / Molar mass
Number of moles of propane (C3H8) = 7.2g / 44.11 g/mol
≈ 0.163 moles
3. Determine the number of moles of hydrogen (H) present in propane (C3H8). This can be done using the stoichiometry of the compound.
In 1 mole of propane (C3H8), there are 8 moles of hydrogen (H). This is based on the balanced chemical equation:
C3H8 → 3CO2 + 4H2O
(Number of moles of H / Number of moles of C3H8) = 8 moles H / 1 mole C3H8
Number of moles of H = (Number of moles of C3H8) * (8 moles of H / 1 mole of C3H8)
= 0.163 moles * 8
≈ 1.304 moles
4. Finally, calculate the number of hydrogen atoms using Avogadro's number, which states that 1 mole of any substance contains 6.022 x 10^23 particles.
Number of H atoms = (Number of moles of H) * (6.022 x 10^23 atoms/mole)
= 1.304 moles * (6.022 x 10^23 atoms/mole)
≈ 7.853 x 10^23 atoms
Therefore, approximately 7.853 x 10^23 hydrogen atoms are present in 7.2g of propane (C3H8).
How many mols C3H8? That's grams/molar mass.
How many molecules C3H8 in that many grams? That's mols x 6.0E23
H atoms = 8x that.