A student has 540.0 mL of a 0.1035 M aqueous solution of Na2CrO4 to use in an experiment. She accidentally leaves the container uncovered and comes back the next week to find only a solid residue. The mass of the residue is 19.12 g. Determine the chemical formula of this residue.

The chemical formula of this residue:

Explanation:

Mass of residue = 19.12

Let the formula of the residue be

Moles of residue: n

Moles of sodium chromate = n'

Molarity of sodium chromate = 0.1035 M

Volume of sodium chromate solution = 540.0 mL = 0.540 L

1 mL = 0.001 L

According to reaction,1 mole of   gives 1 mole of

So, n = n'

x = 10

The chemical formula of this residue:

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.