Vinegar - concentration of ethanoic acid?

Question

If concentration of ehanoic acid in vinegar as % of mass is 5%, what is the molarity of ethanoic acid in undiluted vinegar? The density of vinegar is 1.02 g/cc and RMM of Ethanoic Acid is: 282.05.

Sorry RMM is 60. Thanks Gervald for pointing out my error. The molecular formula of acid is: CH3COOH.

Answer 1

Vinegar 32 pence a bottle in morrison"s,
gives you that information on the lable.

Answer 2

5% by mass of ethanoic acid is equivalent to
50 g/dm^3
Divide this by the RMM of 60 and you get
0.8333 which is the molarity of the ethanoic acid (vinegar)

Answer 3

The Mr of ethanoic acid is 60, by the way.

Answer 4

The key to solving this problem is understanding how chemists express mass and concentration. All weights are expressed in terms of moles. A mole itself is just a number. This many atoms of any element in the periodic table equals its atomic weight. Molecular weights are the sum of atomic weights. The acid in question (acetic acid - no working chemist ever calls it "ethanolic acid") has a chemical formula of C2H4O2. The molecular weight would be 2*12 + 4*1 + 2* 16 = 60 grams/mole. Next, one needs to study chemistry to predict what happens when acetic acid mixes with sodium hydroxide. The chemical equation is: C2H4O2 + NaOH -> C2H3O2Na + H2O All chemists know acid + base = water and salt. The important thing about the equation is it indicates 1 molecule of acetic acid reacts with 1 molecule of sodium hydroxide. Since a mole is just a number, this applies to moles as well. To solve the problem, find the number of moles of sodium hydroxide used to neutralize the acetic acid. This will be the same as the number of moles of acetic acid itself. This is because there is a 1 to 1 relationship between them. Molarity is how chemists express concentration. The units are moles per liter. A 0.2 M solution of NaOH has 0.2 moles per liter. There are 1000 ml in a liter, so (45.00 ml)*(1 liter / 1000 ml) * (0.2 moles / liter) = 0.009 moles of Sodium hydroxide. This is of course also the number of moles of acetic acid. If the initial volume was 15 ml, then (0.009 moles / 15 ml) * (1000 ml / liter) = 0.6 moles / liter. (0.6 moles)*(60 grams/mole) = 36 grams acetic acid per liter. In the metric system weight is equivalent to mass for water, so 1 liter is 1000 grams. 36/1000 = 3.6% by weight. Most vinegar is 2 to 5% acetic acid, so this seems accurate. FYI: Besides using arcane terms to describe very ordinary substances, this problem shows further disresepct to the student by expressing its volume in terms of cm^3. Again, a working chemist would never do this. Dm^3 is also seldom used. This disparity between achademic and working chemistry is one of the reasons I feel chemistry is the worst taught of all the sciences.