How much acetic acid (by weight) is required to obtain 139.05 g of aminoacetic acid ethyl ester at 90% yield?
Aminoacetic acid ethyl ester formula: CH2 (NH2) – COOC2H5
Acetic acid formula – CH3COOH
Aminoacetic acid formula – CH2 (NH2) – COOH
η is the mass fraction of the practical yield of the product from the theoretically possible one.
Let’s write down given:
m (CH2 (NH2) – СООС2Н5) = 139.05 g
η (СН2 (NH2) – СООС2Н5) = 90% or 0.9
Find: m (CH3 COOH) -?
Solution
1) Find the mass of the theoretical yield of ethyl ester of aminoacetic acid:
η = m (practical output) * 100% / m (theoretical output),
m (theoretical output) = m (practical output) * 100% / η
m (theoretical output СН2 (NH2) – СООС2Н5) = 139.05 g * 100% / 90%
m (theoretical output СН2 (NH2) – СООС2Н5) = 154.5 g
2) Calculate the mass of aminoacetic acid, which is necessary to obtain 154.5 g of ether:
Let’s write the reaction equation:
CH2 (NH2) – COOH + C2H5OH → CH2 (NH2) – COOC2H5 + H2O
M (CH2 (NH2) – COOH) = 12 * 2 + 14 + 16 * 2 + 5 = 75 g / mol
М (СН2 (NH2) – СООС2Н5) = 12 * 4 + 16 * 2 + 14 + 9 = 103 g / mol
Let’s compose the ratio:
75 g (CH2 (NH2) – COOH) forms 103 g (CH2 (NH2) – COOC2H5)
X g (CH2 (NH2) – COOH) forms 154.5 g (CH2 (NH2) – COOC2H5)
X = 75g * 154.5g / 103g
X = 112.5 g (CH2 (NH2) – COOH)
3) Calculate the mass of acetic acid:
To obtain 1 mol (CH2 (NH2) – COOH), 1 mol (CH3 COOH) is needed, hence
M (CH3 COOH) = 12 * 2 + 16 * 2 + 4 = 60 g / mol
60 g (CH3 COOH) – 75 g (CH2 (NH2) – COOH)
Y g (CH3 COOH) – 112.5 g (CH2 (NH2) – COOH)
Y = 60g * 112.5g / 75g
Y = 90 g (CH3COOH)
Answer: 90 g (CH3COOH)