Chem.Question.(Uni 1st year)

2012-10-27 12:41 pm

'you have been asked to make up 920 ml of a 33.3% (w/v) solution. How many grams of the compound would you need (to 2 dp)?'

33.3% w/v is it mean 33.3g of A made up to 100mL ?
And whats the method to do this? (no need to write the numerical answer, just use algebras)

更新1:

AND ALSO: Qn2: If you dissolved 95.83 g of a compound in water and made it up to a final volume of 370 ml, what would be the percentage weight by volume (w/v) concentration of the solution (to 2 dp)? Thanks!!

回答 (1)

己式庚辛

2012-11-04 5:44 am

✔ 最佳答案

yes, for w/v (weight-to-volume), you directly divide the mass (in g) by volume (in ml).
of course in the unit like g/ml, they aren't canceling each other, but that's just some convention showing the proportions of solutes in solutions.

other than w/v, there're also w/w and v/v.
w/w : mass of solute / mass of solution, typically used in concentrations of solids and liquids w/v : mass of solute / volume of solution, typically used in concentrations of liquids v/v : volume of solute / volume of solution, typically used in concentrations of liquids and gases
and answer for second question is 25.90%, assuming volume of water doesn't change after dissolution of such a large amount of solid.

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