4. 2 C8H18(g) + 25 O2(g) 16 CO2(g) + 18 H2O(g) at STP
How many moles of O2 are needed to react with 60.0g of C8H18 (octane)?
mole of 02 = 60/114 = 53 mols
2 moles of octane =25 mols of 02
0.53/2 x 25= 6.625 mols
How many litres of CO2 are produced?
16 x 0.53mol/2mol = 4.24 moles
4.24mol x 22.4 L = 94.976 L of co2
Looks OK to me. I might suggest that you correctly rounded to 0.53 for mols O2 for the number of significant figures but you didn't follow that practice for the rest of the problem.
To find the number of moles of O2 needed to react with 60.0g of C8H18 (octane), you can use the molar mass of octane (C8H18) and the balanced equation.
1. Find the molar mass of octane (C8H18):
- C8H18 contains 8 carbon atoms, each with a molar mass of 12.01 g/mol. So, the molar mass of carbon in octane is 8 x 12.01 g/mol = 96.08 g/mol.
- H18 contains 18 hydrogen atoms, each with a molar mass of 1.008 g/mol. So, the molar mass of hydrogen in octane is 18 x 1.008 g/mol = 18.14 g/mol.
- Add the molar masses of carbon and hydrogen to get the molar mass of octane: 96.08 g/mol + 18.14 g/mol = 114.22 g/mol.
2. Use the molar mass of octane to convert grams to moles:
- Divide the given mass (60.0g) by the molar mass of octane (114.22 g/mol): 60.0 g / 114.22 g/mol = 0.524 moles (rounded to 3 decimal places).
3. Use the stoichiometry (from the balanced equation) to find the moles of O2:
- From the balanced equation, you can see that 2 moles of octane reacts with 25 moles of O2.
- Set up a proportion to find the number of moles of O2 needed: (0.524 moles of octane / 2 moles of octane) = (x moles of O2 / 25 moles of O2).
- Cross-multiply and solve for x: x = (0.524 moles of octane * 25 moles of O2) / 2 moles of octane = 6.55 moles of O2 (rounded to 3 decimal places).
So, the number of moles of O2 needed to react with 60.0g of C8H18 (octane) is approximately 6.55 moles.
To find the number of liters of CO2 produced, you can again use the stoichiometry (from the balanced equation) and the molar volume of a gas at STP.
4. Use the stoichiometry to find the moles of CO2:
- From the balanced equation, you can see that 2 moles of octane produce 16 moles of CO2.
- Set up a proportion to find the number of moles of CO2 produced: (0.524 moles of octane / 2 moles of octane) = (x moles of CO2 / 16 moles of CO2).
- Cross-multiply and solve for x: x = (0.524 moles of octane * 16 moles of CO2) / 2 moles of octane = 4.19 moles of CO2 (rounded to 2 decimal places).
5. Use the molar volume of a gas at STP (22.4 L/mol) to convert moles of CO2 to liters of CO2:
- Multiply the number of moles of CO2 (4.19 moles) by the molar volume (22.4 L/mol): 4.19 moles * 22.4 L/mol = 94.016 L of CO2 (rounded to 3 decimal places).
So, the number of liters of CO2 produced is approximately 94.016 L.