when 21.6g of carbon were burned in the presence of 73.9g of oxygen 16.3g of oxygen remain unreacted. What mass of carbon dioxide was produced

If some O2 remains unreacted, then C is the limiting reagent.

mols C = grams/atomic mass = ?
Using the coefficients in the balanced equation, convert mols C to mols CO2.
Now convert mols CO2 to grams. g = mols x molar mass

To determine the mass of carbon dioxide produced, we need to calculate the amount of oxygen consumed during the combustion reaction.

First, we need to find the number of moles of oxygen that reacted. We can use the molar mass of O₂, which is 32 g/mol.

Number of moles of O₂ used = mass of oxygen used / molar mass of O₂
Number of moles of O₂ used = 73.9 g / 32 g/mol
Number of moles of O₂ used = 2.31 mol

Since the balanced chemical equation for the combustion of carbon is:

C + O₂ -> CO₂

We can determine the stoichiometric ratio of oxygen to carbon dioxide from the balanced equation, which is 1:1. This means that 1 mole of oxygen reacts to produce 1 mole of carbon dioxide.

Now, we can determine the number of moles of carbon dioxide produced:

Number of moles of CO₂ produced = Number of moles of O₂ used
Number of moles of CO₂ produced = 2.31 mol

Finally, we can convert the moles of carbon dioxide to grams using the molar mass of CO₂, which is 44 g/mol:

Mass of CO₂ produced = Number of moles of CO₂ produced × molar mass of CO₂
Mass of CO₂ produced = 2.31 mol × 44 g/mol
Mass of CO₂ produced = 101.64 g

Therefore, the mass of carbon dioxide produced is approximately 101.64 grams.