Need help stepping through this for a review.

Question

I need to prepare 40grams of a 29% sugar solution. How do I calculate how much sugar and how much water is needed?
Was given this formula:

weight% (w/w)=100 * (mass of solute/total mass of solution)

I set up my problem:

.29 = 100* (x/40)
.116 = x

This answer doesn't make sense to me and I still am unsure how much water or how much sugar to use.

Any help is really appreciated!!

Answer 1

Thanks for showing your work. It helps spot the problem which is that you should have substituted 29 for 29%. The 100 is in the formula to convert that 0.29 to 29% or
29 = 100(x/40). You can omit the 100 and use
0.29 = (x/40)
In other words, your answer is just 100x to small. You should use 11.6g sugar.
How much H2O. Since the solution must weigh 40g, then the H2O must be 40-11.6 = ?

Answer 2

Oh my gosh thank you!! I knew it was something simple I was missing. Being back in school after so many years is definitely making my brain work again.

So then the amt of H2O=4 0 -11.6
H20= 28.4mL

Thank you again for taking the time to help!!

Answer 3

Yes, again thanks for showing your work. It really helps spot the problem quickly. I which more students would do that. It would make it easier for them but they don't want to take the time it takes to type it out. Which makes us take the time to type it which means we spend more time typing and less time answering questions.