If a chemist has a stock solution of HBr that is 10.0 M and would like to make 450.0 mL of 3.0 M HBr, how would he or she do it?
How many moles do you need in the final solution? That is M x L = x moles
You want that many mols of the stock solution. You know is it 10 M; therefore, 10 M x ?L = x moles.
Solve for ?L.
You may be more comfortable using the dilution formula.
c1v1 = c2v2
c= concn
v = volume
To create a 450.0 mL solution of 3.0 M HBr from a 10.0 M stock solution of HBr, the chemist would need to perform a dilution. Dilution involves adding a calculated volume of the stock solution to a calculated volume of solvent (usually water) to achieve the desired concentration.
Here's how the chemist could proceed:
1. Use the dilution formula C1V1 = C2V2, where C1 is the initial concentration, V1 is the initial volume, C2 is the final concentration, and V2 is the final volume.
2. Rearrange the formula to solve for V1: V1 = (C2 * V2) / C1.
3. Plug in the values into the equation to find the volume of the stock solution needed: V1 = (3.0 M * 450.0 mL) / 10.0 M.
4. Calculate the volume of the stock solution required: V1 = 135.0 mL.
5. Measure 135.0 mL of the 10.0 M stock solution of HBr using a volumetric pipette or graduated cylinder.
6. Transfer the measured 135.0 mL of the stock solution into a clean, empty container.
7. Add enough solvent (usually water) to the container to reach a final volume of 450.0 mL. This can be done by carefully adding water and bringing the solution up to the desired volume using a volumetric flask or measuring cylinder.
8. Thoroughly mix the solution to ensure complete homogeneity.
Now the chemist will have successfully prepared 450.0 mL of a 3.0 M HBr solution by diluting the 10.0 M stock solution.