solving a reactant with a chemical reaction

Question

Wine goes bad soon after opening because the ethanol CH3CH2OH in it reacts with oxygen gas O2 from the air to form water H2O and acetic acid CH3COOH, the main ingredient of vinegar.

What mass of acetic acid is produced by the reaction of 5.1g of oxygen gas?

Answer 1

First, it is helpful to translate the language into a balanced chemical equation:

CH₃CH₂OH + O₂ → H₂O + CH₃COOH

(ethanol) (acetic acid)

Are my Carbons, Hydrogens, and Oxygens balanced on the reactants side (left side) and the products side (right side)?

Reactants side: | Products side:

2C | 2C

6H | 6H

3O | 3O

Yes! This step was performed to ensure that no coefficients are needed to balance the chemical equation. In the future, some of the problems you will tackle will include mole ratio conversions with coefficients other than 1.

The question: What mass of acetic acid is produced by the reaction of 5.1g of oxygen gas?

First, identify your start and end points:

What are you starting out with? 5.1 g of oxygen gas

What will you end with? mass of acetic acid

Next, familiarize yourself with the following conversions:

<------------ <------------

grams ------------> moles ------------> atoms (or particles)

*to convert from *in the future, *to convert from

g to mol, use mol to mol mol to atoms, use

molar mass from conversions Avogadro's constant

the periodic table occur at this

step

You will be using the grams to moles conversion (left side). In addition, refer to the balance chemical equation, for every 1 mole of O₂ reacted, 1 mole of acetic acid is produced.

Next, find the molar mass of O₂ and acetic acid using the periodic table.

molar mass of oxygen = 15.999 g/mol

molar mass of carbon = 12.011 g/mol

molar mass of hydrogen = 1.008 g/mol

so, molar mass of O₂ = 15.999 x 2 = 31.998 g/mol

so, molar mass of CH₃COOH = [ (12.011 x 2) + (1.008 x 4) + (15.999 x 2) ] = 60.052 g/mol

Finally, set-up your 'rail road tracks.' Hint: set up your 'tracks' to ensure cross cancelation of units. Don't forget to always use units and the compound you are referring to :

5.1 g O₂ | 1 mol O₂ | 1 mol CH₃COOH | 60.052 g CH₃COOH

-------------------------------------------------------------------------------------------- = 9.6 g CH₃COOH (*2 sig figs)

| 31.998 g O₂ | 1 mol O₂ | 1 mol CH₃COOH