Question

If the mass of the baking soda before the reaction was 10 grams and the mass of the vinegar was 15 grams and all of the baking soda and vinegar completely reacted, what would the mass of the products be? (Remember the law of conservation of matter)

Answer 1

Answer:

8.946g NaHCO₃,

14.475g H₂O,

1.025g CH₃COO⁻Na⁺,

0.500g CO₂.

Explanation:

Baking soda (NaHCO₃) reacts with vinegar (CH₃COOH 5%) producing  CH₃COO⁻Na⁺, H₂O and CO₂, thus:

NaHCO₃ + CH₃COOH → CH₃COO⁻Na⁺ + H₂O + CO₂

10g of NaHCO₃ are:

10g × (1mol / 84g) = 0.119 moles NaHCO₃

Moles of CH₃COOH in 15g of vinegar are:

15g vinegar × 5% = 0.75g CH₃COOH × (1mol / 60g) = 0.0125moles CH₃ COOH

After reaction, moles of NaHCO₃ that remains are:

0.119mol - 0.0125mol = 0.1065 moles NaHCO₃

In mass:

0.1065mol ₓ (84g / 1mol) = 8.946g NaHCO₃

Acetic acid reacts completely producing  0.0125moles of CH₃COO⁻Na⁺, water and CO₂. In mass:

CH₃COO⁻Na⁺ = 0.0125mol ₓ (82.03g / 1mol) = 1.025g CH₃COO⁻Na⁺

H₂O = 0.0125mol ₓ (18.01g / 1mol) = 0.225g H₂O

CO₂ = 0.0125mol ₓ (40g / 1mol) = 0.500g CO₂

Now, 95% of vinegar is water (Doesn't react), that is:

15g × 95% = 14.25g H₂O. Total mass of water is:

14.25g + 0.225g = 14.475g H₂O

Total mass is:

8.946g + 14.475g H₂O + 1.025g + 0.500g ≈ 25g. The same than initial mass following law of conservation of matter.