Question

How many grams of a stock solution that is 92.5 percent H2SO4 by mass would be needed to make 250 grams of a 35.0 percent by mass solution? Show all of the work needed to solve this problem.

Answer 1

just by mass word drives me crazy lol
let me check

Answer 2

here is the formula

Answer 3

because the concentrations given are the same, you can use the thinking applied to \(C_1V_1=C_2V_2\).

So the formula you would use is \(C_1m_1=C_2m_2\)

where C is concentration and m is mass.

Answer 4

so that means
% by mass= (Mr of compound* mole of element in compound) / (Mr of compound) * 100

Answer 5

that beautiful cursive though

Answer 6

So I have to find Mr of H2SO4?

Answer 7

just a sec
@aaronq where are concentrations?? i kinda lost u

Answer 8

92.5 percent H2SO4 by mass is a concentration, it's just given in terms of mass and not volume like you usually see.

Answer 9

owhhhhhh i didn't know that

Answer 10

you can do it the way you're proceeding, and i would suggest you do, but the formula i posted is a shortcut.

Answer 11

i don't understand my own post lol @aaronq

Answer 12

I'm so confused lol

Answer 13

so if we go with your formula
it'll be
92.5* X= 35.0* 250
?@aaronq

Answer 14

im trying to understand so that im able to explain to u @yesy7 lol

Answer 15

yep

Answer 16

okay then your way is piece of cake lol
but the formula that i posted a pic of is piece of pain
could you kinda help me understand it? @aaronq

Answer 17

@yesy7 apparently percentage by mass can be taken as concentration, and since they gave you 2 % by masses and 1 mass in grams and they ask u to find other mass
u can use the formula @aaronq gave

C1m1= C2m2

im guessing you are using this because solution is same in both cases?

Answer 18

Oh okay, seems much easier. So it would be set up like how you posted up there ^^?

Answer 19

yup :3

Answer 20

@Somy If you wanted to do it the other way, you would use the formula in the picture to find moles of 250 grams of a 35.0 percent by mass solution.

Then using the same formula, find the moles to find the moles of the stock solution (92.5 percent H2SO4) you need, then convert that to mass.

Answer 21

this is a thing.....it sounds easy
but...im kinda cursed, i don't get easy stuff
let me try what you are saying @aaronq

Answer 22

So it would look like this 92.5 * X=8750 (idk what to do with the x)...

Answer 23

oh this part is math

Answer 24

92.5X= 8750
x= 8750/ 92.5
x=

Answer 25

solve for x?

Answer 26

yes

Answer 27

So it's 94.6

Answer 28

wow that was much easier

Answer 29

ikr lol