Question

I have 370 grams of paraformaldeyhde and i want to make a 37% formaldeyhde solution out of this amount ?.

Answer 1

Heat the paraformaldehyde with 990 mL water.

Explanation:

Paraformaldehyde is a polymer of formaldehyde with the formula `"HO"("CH"_2"O")_n"H"`, where `n = "8-100"`.

You can depolymerize paraformaldehyde and form a formaldehyde solution by heating it with water.

Assume that `n = 100`.

Then

`M_text(r):color(white)(mmll)3020.61color(white)(mmmmm) 30.03`
`color(white)(mmm)"HO"("CH"_2"O")_100"H" → 100"CH"_2"O + H"_2"O"`

Calculate the mass of formaldehyde

`370 color(red)(cancel(color(black)("g paraformaldehyde"))) × (1 color(red)(cancel(color(black)("mol paraformaldehyde"))))/(3020.61 color(red)(cancel(color(black)("g paraformaldehyde")))) × (100 color(red)(cancel(color(black)("mol formaldehyde"))))/(1 color(red)(cancel(color(black)("mol paraformaldehyde")))) × "30.03 g formaldehyde"/(1 color(red)(cancel(color(black)("mol formaldehyde")))) = "368 g formaldehyde"`

In other words, depolymerization of a given mass of paraformaldehyde produces approximately the same mass of formaldehyde.

Calculate the mass of water required

`"Mass of water" = 368 color(red)(cancel(color(black)("g formaldehyde"))) × "100 g water"/(37 color(red)(cancel(color(black)("g formaldehyde")))) = "990 g water"`

Thus, you heat the paraformaldehyde with 990 mL water.