How do I calculate the substrate concentration of a solution?

Question

When I add 0.1ml of 4mM substrate to a 3.9ml solution???

Answer 1

concentration is moles/L

0.1mL=10^-4L
4mM is 4x10^-3 mol/ L

So if you have 0.1mL of that 4mM solution, multiply to get how many moles of substrate (solute) you have

4x10^-3 x 1 x10^-4 = 4x10^-7 mol.

Now you already have a 3.9mL solution (does it have anything dissolved in it?) I'll assume not since you didn't say so...

So now you have 4mL total, the 0.1 you added and the original 3.9. You have 4x10^-7 mol of stuff you added, so concentration is:

moles/L = 4x10^-7moles/4x10^-3 L =1 x 10^-4 M solution

Answer 2

Calculate the substrate concentration of a beverage that contains 18 g of sucrose per 8 oz. (240 ml) serving