Stoichiometric table for benzaldehyde + acetone and NaOH. From a study guide, I

Question

Stoichiometric table for benzaldehyde + acetone and NaOH. From a study guide, I just want to make sure I'm doing it right. If possible, a detailed explanation of finding the LR, theoretical yield, and molar equivalence. Especially molar equivalence.

Now, you try this one! Note: Do not assume NaOH is catalytic here... CHO NaOH (aa) EtOH CH CH dibenzalacetone benzaldehyde acetone (densi ty 1.045 g/mL0 (d 0.791 g/mL) (1,5-diphenyl 1,4-pentadien-3-one) ms.p 110.5 -112°C Molar Mass Density Amount Used mmol molar Reagent (g/mol) (g/mL) equivalents (2 sig figs) 1.045 106.12 5.1 mL benzaldehyde 0.791 50.08 2.0 mL acetone N/A 5.0 g NaOH 40.00 Theoretical yield: Limiting reagent:

Explanation / Answer

Benzaldehyde mmol can be calculated as follows:

Benzaldehyde mmol = Wt. of benaldehyde / molar mass

Benzaldehyde mmol = (Volume x density) / molar mass

Benzaldehyde mmol = (5.1mL x 1.045g/mL) / (106.12g/mol)

Benzaldehyde mmol = 0.050mol

Benzaldehyde mmol = 50mmol

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Acetone mmol can be calculated as follows:

Acetone mmol = (Volume x density) / molar mass

Acetone mmol = (2.0mL x 0.791g/mL) / (50.08g/mol)

Acetone mmol = 0.032 mol

Acetone mmol = 32 mmol

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NaOH mmol can be calculated as follows:

NaOH mmol = Weight / molar mass

NaOH mmol = (5.0 g) / (40.00g/mol)

NaOH mmol = 0.125 mol

NaOH mmol = 125 mmol

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Molar equivalents can be calculated by dividing all the mmol by smallest mmol number i.e. 32.

Thus, molar equivalent of benzaldehyde = 50/32 = 1.6

Molar equivalent of acetone = 32/32 = 1.0

Molar equivalent of NaOH = 125 / 32 = 3.9

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Limiting reagent is the reactant that is limited. As per the balanced equation, 2 moles of benzaldehyde requires 1 mole of acetone. 1.6 equivalent of benzaldehyde will require 1.6/2 = 0.8 equivalent of acetone. However, equivalent of acetone avalibale is 1.0 (excess). Thus, in given reaction, benzaldehyde is the limiting reagent.

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Theoretical yield = (Molar mass of dibenzalacetone / (2 x molar mass of benzaldehyde)) x mass of benzaldehyde

Theoretical yield = (234.29 / (2 x 106.12)) x (5.1mL x 1.045g/mL)

Theoretical yield = (234.29 / 212.24) x (5.33g)

Theoretical yield = 5.9 g

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