2‑Propanol (CH3CHOHCH3) is oxidised by sodium dichromate (Na2Cr2O7·2H2O) in acidic medium to give acetone. If 5.0 g of 2‑propanol are used, how many moles of acetone will be formed assuming quantitative conversion?
Answer
0.083 mol
The correct answer is 0.083 mol — Round to three significant figures: 0.083 mol.
Step-by-step solution
- Write the oxidation reaction: CH3CHOHCH3 → CH3COCH3 + 2 H⁺ + 2 e⁻ (overall balanced with dichromate).
- Note that one mole of 2‑propanol yields one mole of acetone; the stoichiometric coefficient is 1:1.
- Calculate moles of 2‑propanol: Molar mass = 60.10 g·mol⁻¹, moles = 5.0 g / 60.10 g·mol⁻¹ = 0.0832 mol.
- Since conversion is quantitative, moles of acetone formed = moles of 2‑propanol = 0.0832 mol.
- Round to three significant figures: 0.083 mol.
Common mistake: Assuming that the dichromate is the limiting reagent; the problem states excess oxidant.
Concept tested: Oxidation of secondary alcohols to ketones
Published · How this solution was prepared and checked
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