I am confused as to how to solve the below problem. I am not sure which formula to use. At first I thought I calculate the molar mass of NaOH, followed by calculating moles of NaOH. But I don't have the mass of NaOH to calculate moles. Do I convert 10mL to grams to Be able to calculate moles and then the molarity? OR do I use Ci x Vi = Cf x Vf, to solve for the molarity?
If 2.0 ml of 0.010 M of NaOH is mixed with enough water to make the total volume 8mL, what is molarity of the resulting solution?
There are numerous ways to do this but the shortest way is to use the dilution formula that you have in the last sentence of your post.
I even take a short cut with that.
0.01M NaOH x (2.0 mL/8 mL) = ? M.
Note: It isn't needed, but you really do have the mass.
moles NaOH = M x L = ?
Then mols NaOH = grams NaOH/molar mass NaOH.
Knowing mols NaOH and molar mass you can calculate grams.
To solve this problem, you can use the formula Ci x Vi = Cf x Vf, which is the formula for dilution calculations. Here's how you can apply it step by step:
1. Identify the given values:
- Initial concentration (Ci): 0.010 M
- Initial volume (Vi): 2.0 mL
- Final volume (Vf): 8.0 mL
2. Convert the initial volume to liters:
- 2.0 mL = 2.0 x 10^-3 L (as there are 1000 mL in 1 L)
3. Use the formula Ci x Vi = Cf x Vf to solve for the final concentration (Cf):
- Ci x Vi = Cf x Vf
- (0.010 M) x (2.0 x 10^-3 L) = Cf x (8.0 x 10^-3 L)
- Rearranging the equation to solve for Cf gives:
Cf = (Ci x Vi) / Vf
4. Plug in the values and calculate the final concentration:
- Cf = (0.010 M x 2.0 x 10^-3 L) / (8.0 x 10^-3 L)
- Cf = 0.0025 M
Therefore, the molarity of the resulting solution is 0.0025 M.
Note: It is not necessary to calculate the molar mass of NaOH or convert mL to grams in order to find the molarity. The given information already includes the molarity (0.010 M) and volumes (2.0 mL and 8.0 mL) needed for the dilution calculation.