The average weight of a \"normal\" black ant is 0.0050 g. In its metabolism an a

ID: 824361 • Letter: T

Question

The average weight of a "normal" black ant is 0.0050 g. In its metabolism an ant generates formic

acid, HCOOH (a monoprotic acid of MW= 46 g/mol), which is the cause of the welt resulting from its

bite. Suppose 1000 ants are collected and put into a press to squeeze out the formic acid quantitatively.

The formic acid is diluted to 100.0mL with water, and the titration of this solution requires 9.90 mL of

a 0.100 M solution of NaOH. Calculate the weight percentage of formic acid in an average ant.

The average weight of one ant = 0.005 g

Avg. weight of 1000 ants = 5 g

Now for titration we use the formula:

a x M1 x V1 = b x M2 x V2

where,

M1, M2 = molarity

V1, V2 = volumes

a = acidity of formic acid = 1 (as only one H+)

b = basicity of NaOH = 1

Thus,

1 x M1 x 100 = 1 x 9.9 x 0.1

M1 = conc. of formic acid = 0.0099 M

0.0099 M ----> 0.1 L of solution

No. of moles = 0.00099 moles = 0.0455 g in 5 g of ants

Thus in 0.005 g ----> 4.55 x 10^-5 g formic acid

thus weight percentage = 0.91 %

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