[raccoon]

I haven't taken a chem class and my prof is essentially useless. Any help is appreciated.

1.

10NaClO2 + 5H2SO4 --> 8ClO2 + 5Na2SO4 + 2Hcl + 4H20

What mass of NaClO2 is needed to generate enough ClO2 to treat 1.0 x 10^5 m^3 of water with 2.9 ppm of ClO2 is the present yield of the reaction is 94%.

2. A commercial gas mix is 87% isooctane, 3% heptane, and 10% ethanol by weight. If the density of the gas is 0.755 g/mL what is the mass of CO2 produced by the combustion of one litre of gas. If a vehicle is rated at 5.5 L of gas for each 100km driven how much Co2 would be prod'd by a 13.2km round trip?

3. Compare the CO2 emissions in tonnes per GJ for wood pellets and natural gas. Wood pellets have an energy density of 4.8 MWh/tonne. Assume that the wood pellets have a water content of 6% and an empirical formula of CH2O. The heat of vaporization of water has already been taken into account in the determination of the energy density of the wood pellets. Natural gas has an energy density of 53..6 MJ/kg and may be assumed to be pure methane.

[sjb]

I haven't taken a chem class and my prof is essentially useless. Any help is appreciated.

1.

10NaClO₂ + 5H₂SO₄ --> 8ClO₂ + 5Na₂SO₄ + 2HCl + 4H₂O

What mass of NaClO₂ is needed to generate enough ClO₂ to treat 1.0 x 10⁵ m³ of water with 2.9 ppm of ClO₂ is the present yield of the reaction is 94%.

2. A commercial gas mix is 87% isooctane, 3% heptane, and 10% ethanol by weight. If the density of the gas is 0.755 g/mL what is the mass of CO₂ produced by the combustion of one litre of gas. If a vehicle is rated at 5.5 L of gas for each 100km driven how much CO₂ would be prod'd by a 13.2km round trip?

3. Compare the CO₂ emissions in tonnes per GJ for wood pellets and natural gas. Wood pellets have an energy density of 4.8 MWh/tonne. Assume that the wood pellets have a water content of 6% and an empirical formula of CH₂O. The heat of vaporization of water has already been taken into account in the determination of the energy density of the wood pellets. Natural gas has an energy density of 53..6 MJ/kg and may be assumed to be pure methane.

Please show your attempts, this is a forum rule.

[raccoon]

#1. I had only got to the number of moles ClO2. Via:

2.9ppm ClO2 = 2.9 mg/L x 10-3 g/mg x 1 mol ClO2/67.45 g ClO2 x 103 L/m3 x 1.0x105 m3 H2O

= 4299.48 mol ClO2

Not sure where to go from there.

#2 I converted the density to 755 g/L and multiplied that by 0.87 (the gas was 87% isooctane) for isooctance giving 656.85 g/L.

656.85 g/L x (1 mol C8H18/114.23 g) x (8 mol CO2/1 mol C8H18) x (44g CO2/1 mol CO2) = 2024.1 g/L CO2
Do for both heptane to get 69.6 g/L CO2 and ethanol to get 144 g/L CO2. Add the three to get 2237.7 g/L CO2
Multiply that by the result of 5.5 L/100 km --> 0.055L/km x 13.2 km = 0.726 L gas used
0.726 L x 2237.7 g/L CO2 = 1624.6 g CO2

?

For #3 I am hung up on using an example mass and then converting to get the moles of CO2. So for 15g of CH2O do I multiply that by the stoichiometric values or do I need molar mass?