The hint isn't quite right but close.
You want 40% formaldehyde (w/w) which means 40g HCHO/100 g solution =
40 g HCHO/(40g HCHO + 60 H2O)
[425g HCHO/x]*100 = 40%
Solve for x which is the TOTAL grams solution. The amount of H2O to add will be x-425 = ? or 637.5g H2O.
Check it to see if that will do it.
[425/(425+637.5)]*100 =
(425/1062.5)*100 = 40%
what mass of water must be added to 425 g of formaldehyde to prepare a 40.0% (by mass) solution of formaldehyde? this solution, called formalin, is used to preserve biological specimens.
(hint:) substitute the known quantities into the definition for mass percent, and then solve for the unknown quantity (mass of solvent)
2 answers
ohhh yes, you are right. thank you very much I see my mistake now thank you again. have a nice day (:
1 answer