Question

Consider the reaction. How many grams of carbon should be burned in an excess of oxygen at STP to obtain 2.21 L of carbon dioxide? 1.18 g 2.21 g 4.12 g 4.34 g

Answer 1

You must burn 1.17 g C to obtain 2.21 L CO₂ at STP.

The balanced chemical equation is

C + O₂ → CO₂.

Step 1. Convert litres of CO₂ to moles of CO₂.

STP is 0 °C and 1 bar. At STP the volume of 1 mol of an ideal gas is 22.71 L.

Moles of CO₂ = 2.21 L CO₂ × (1 mol CO₂/22.71 L CO₂) = 0.097 31 mol CO₂

Step 2. Use the molar ratio of C:CO₂ to convert moles of CO₂ to moles of C

Moles of C = 0.097 31mol CO₂ × (1 mol C/1 mol CO₂) = 0.097 31mol C

Step 3. Use the molar mass of C to calculate the mass of C

Mass of C = 0.097 31mol C × (12.01 g C/1 mol C) = 1.17 g C

It looks as if you are using the old (pre-1982) definition of STP. That definition gives a value of 1.18 g C.

Answer 2

Answer:

1.18

Explanation:

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