danielle p.

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...

ohhh yes, you are right. thank you very much I see my mistake now thank you again. have a nice day (:

thank you Dr. Bob! I get it know.

thanks (: