Question

C3H8 + 5O2 ---> 3CO2 + 4H2O

How many grams of carbon dioxide are produced from the reaction of 100.0g of propane? How many molecules of carbon dioxide are produced?

Cl2O7 + H2O ---> 2HClO4

How many grams of water are needed to react completely with 77.6 g of dichlorine heptaoxide? How many molecules of water are needed?

Answer 1

1) it is clear from balanced chemical equation that 1 mole of propane gives 3 moles of CO2. Let us now first calculate the number of moles of propane used

The molecular weight of propane is 44.1 g/mol

Number of moles of propane = weight/ molecular weight

= 100 g / 44.1 g/mol

= 2.267 moles

Number of moles of CO2 produced = 3 x moles of propane

= 3 x 2.267 = 6.80

The molecular weight of CO2 is 44.01 g/mol

Mass of CO2 produced = moles produced x molecular weight

= 6.80 mol x 44.01 g/mol

= 299.4 grams

Number of molecules of CO2 produced = moles x Avagadro's number

= 6.80 moles x 6.022 x 10²³

= 41.43 x 10²³ molecules

2) Let us first calculate number of moles of Cl2O7 . The molecular weight of Cl2O7 is 182.9 g/mol

Moles of Cl2O7 = weight / molecular weight

= 77.6 g / 182.9 g/mol

= 0.424 moles

As from the balanced chemical equation it is clear that 1 mole of Cl2O7 consumes 1 mole of water.

Therefore, 0.424 moles of H2O will be need to completely consume 0.424 moles of Cl2O7. Now let us calculate the weight of H2O in grams. Molecular weight of H2O is 18 g/mol

Mass of H2O = moles x molecular weight

= 0.424 mol x 18 g/mol

= 7.64 grams

Molecules of H2O needed = moles x Avagadro's number

= 0.424 x 6.022 x 10²³

  = 2.55 x 10²³ molecules of H2O