A student wants to burn a 1.25 mL sample of ethanol (C2H5OH, d = 0.789 g/mL) in a jar containing dry air. Assuming the air in the jar is at standard atmospheric pressure and room temperature (22 °C), what volume will the jar need to be in order to hold enough oxygen for complete combustion? Hint: Refer to the composition of dry air in the previous question. (a) Write a balanced chemical reaction for the combustion of ethanol. (b) Calculate the moles of oxygen needed to completely combust the ethanol. (c) Calculate the partial pressure of oxygen in the jar. (d) Calculate the volume of oxygen (in L) needed in t

The volume of the jar needed in order to hold enough oxygen for complete combustion is 24.2 L

(a) C₂H₅OH  + 2O₂ -------> 2CO₂ + 3H₂O

(b)  The moles of oxygen needed to completely combust the ethanol is      0.0429 moles

(c) The Partial pressure of oxygen is 4346.84 Pa

(d) the volume of oxygen (in L) needed in the jar is 1.038 L

Explanation:

Given;

volume of ethanol, V = 1.25 mL

density of ethanol, ρ = 0.789 g/mL

mass of ethanol, m = ρV = (1.25 mL) x (0.789 g/mL) = 0.986g

The volume of the dry air is calculated as;

(a) a balanced chemical reaction for the combustion of ethanol

C₂H₅OH  + 2O₂ -------> 2CO₂ + 3H₂O

(b) The moles of oxygen needed to completely combust the ethanol.

(c) the partial pressure of oxygen in the jar

Total pressure of air in the jar, Pt = 101,325 Pa

Partial pressure of oxygen = nPt

                                            = 0.0429 x 101,325 Pa = 4346.84 Pa

(d) the volume of oxygen (in L) needed in the jar

Total volume of air in the jar = 24.2 L

The fraction of this volume by oxygen = 0.0429 mols x 24.2 L = 1.038 L