Question

page 2 of 4
dp alum : kal(so₄)₂·12h₂o ap alum + 3h₂(g) = 6 - hydrogen

1. calculate the % atom economy for this synthesis - use the example given on page 4 of the experiment instructions as a guide. use the overall net reaction shown in box 1 of the instructions. when calculating the atom economy, calculate your molar masses to the nearest 0.1 g/mol.

formula weight desired / formula of all products × 100 = ae%
(handwritten: 2(474.4g) = 948.8 g/mol; 6(1.01g) = 6.06g/mol; 948.8g + 6.06g = 954.86g/mol; 954.86g/mol kal(so₄)₂·12h₂o / (954.86g/mol kal(so₄)₂·12h₂o + 6.06g/mol h₂) = 0.9937 × 100 = 99.4%)

1. calculate the % overall efficiency for your yield in this synthesis.

% oe = yield (#4) × ae (#5) × 100%
(handwritten: 0.768 × 0.994 × 100% = 76.3%)
reflection questions

1. for many chemical reactions, even under the best of circumstances, it is difficult to achieve reaction yields close to 100%. which step in this alum synthesis procedure is most responsible for a low yield? justify your answer.

Explanation:

Reflection Question 1 Explanation:

To determine the step responsible for low yield in alum synthesis, we analyze common synthesis steps (e.g., precipitation, filtration, crystallization, or reaction kinetics). A key step with potential losses is crystallization (or filtration/transfer steps). During crystallization, some alum may remain dissolved in the solution (mother liquor) instead of precipitating. Alternatively, transfer steps (e.g., moving the precipitate, washing) can cause product loss. Justification: If the solution is not cooled sufficiently or the solvent volume is too high, solubility keeps alum dissolved, reducing recovered yield. Filtration/washing might also lose solid product (e.g., fine crystals passing through filter paper or adhering to glassware).

Reflection Question 1 Answer:

A critical step for low yield is crystallization (or filtration/transfer). Justification: Alum may remain dissolved in the mother liquor (insufficient cooling or excess solvent) instead of precipitating, or product is lost during filtration/washing (e.g., fine crystals pass through filter paper or stick to glassware), reducing the amount of recovered alum.

Answer:

Reflection Question 1 Explanation:

To determine the step responsible for low yield in alum synthesis, we analyze common synthesis steps (e.g., precipitation, filtration, crystallization, or reaction kinetics). A key step with potential losses is crystallization (or filtration/transfer steps). During crystallization, some alum may remain dissolved in the solution (mother liquor) instead of precipitating. Alternatively, transfer steps (e.g., moving the precipitate, washing) can cause product loss. Justification: If the solution is not cooled sufficiently or the solvent volume is too high, solubility keeps alum dissolved, reducing recovered yield. Filtration/washing might also lose solid product (e.g., fine crystals passing through filter paper or adhering to glassware).

Reflection Question 1 Answer:

A critical step for low yield is crystallization (or filtration/transfer). Justification: Alum may remain dissolved in the mother liquor (insufficient cooling or excess solvent) instead of precipitating, or product is lost during filtration/washing (e.g., fine crystals pass through filter paper or stick to glassware), reducing the amount of recovered alum.