Question

in the lab you grind up 2.205 g of an unknown compound and dissolve it in 250 mL of water. You take 5 ml of this solution and dilute it to a volume of 125 mL. using titration, you measure the concentration of the resulting solution to be 1.96*10^-3 M. Determine which of the following could be the formula of the compound. N2O4 P4O10 C6H12O6 MnO2 UF6 I found some answers already but i want a more detailed explination please.

Answer #1

Given:

M2 = 1.96*10^-3 M

V1 = 5 mL

V2 = 125 mL

use:

M1*V1 = M2*V2

M1 = (M2 * V2) / V1

M1 = (1.96*10^-3*125)/5

M1 = 0.049 M

This is the concentration of original solution

volume , V = 2.5*10^2 mL

= 0.25 L

use:

number of mol,

n = Molarity * Volume

= 4.9*10^-2*0.25

= 1.225*10^-2 mol

mass(solute)= 2.205 g

use:

number of mol = mass / molar mass

1.225*10^-2 mol = (2.205 g)/molar mass

molar mass = 180 g/mol

This is molar mass of compound

which is same as molar mass of C6H12O6

So, the compound is C6H12O6

Answer: C6H12O6

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