To neutralize a portion of 9% table vinegar, 90 g of a 20% sodium hydroxide solution were needed. Find the mass (in grams) of the vinegar serving.
We compose the reaction equation:
CH3COOH + NaOH = CH3COONa + H2O.
1) Find the mass of the solute of caustic soda in its solution. To do this, we multiply the mass fraction of the substance by the mass of the solution and divide by one hundred percent: 90 * 20/100 = 18g.
2) Molar mass of caustic soda: 23 + 1 + 16 = 40.
3) The amount of caustic soda substance: 18/40 = 0.45 mol.
4) According to the reaction equation, one mole of sodium hydroxide accounts for one mole of vinegar. This means that the amount of table vinegar substance is 0.45 mol.
5) Molar mass of vinegar: 12 + 3 + 12 + 16 + 16 + 1 = 60.
6) The mass of the vinegar solution: 60 * 0.45 = 27g.
7) The mass of the dissolved substance of vinegar: 27 * 9/100 = 2.43g – the answer.
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