You need 520. mL of a 15 % (m/v) glucose solution. If you have a 25% (m/v) glucose solution on hand, how many milliliters do you need?

0.15 x 520 = 0.25 x mL

To find out how many milliliters of the 25% glucose solution you need, you can use the following formula:

%1 × V1 = %2 × V2

Where:
%1 = percentage of the first solution (25%)
V1 = volume of the first solution (unknown)
%2 = percentage of the second solution (15%)
V2 = volume of the second solution (520 mL)

Using this formula, we can rearrange it to find V1:

V1 = (%2 × V2) / %1

Plugging in the values, we get:

V1 = (15% × 520 mL) / 25%

Simplifying this expression gives us:

V1 = (0.15 × 520) / 0.25

V1 = 78 mL

Therefore, you will need 78 mL of the 25% glucose solution.

To solve this problem, we need to use a dilution formula based on the principle of concentration. The formula is:

C1V1 = C2V2

Where:
C1 = initial concentration of the solution 1
V1 = initial volume of the solution 1
C2 = final concentration of the solution 2
V2 = final volume of the solution 2

In this case, we have:
C1 = 25% (m/v) glucose solution
C2 = 15% (m/v) glucose solution
V2 = 520 mL

We need to find V1, the initial volume of the 25% glucose solution.

Rearranging the formula, we have:
V1 = (C2V2)/C1

Now, let's substitute the values into the formula:

V1 = (0.15 * 520) / 0.25
V1 = (78) / 0.25
V1 = 312 mL

Therefore, you need 312 mL of the 25% (m/v) glucose solution in order to obtain 520 mL of a 15% (m/v) glucose solution.