A chemist dissolves 0.096 g of CuSO4 · 5 H2O in water and dilutes the solution to the mark in a 500-mL volumetric flask. A 10.8-mL sample of this solution is then transferred to a second 500-mL volumetric flask and diluted. What is the molarity of CuSO4 in the second solution?
My Work:
Mass of CuSO4.5H2O per mL = 0.096/500g
mass in 43.6mL = 0.096/500 x 10.8 g = 0.0083712
That is put into 500mL for second flask, so mass per liter = 0.096/500 x 10.8 x 2g
To find molarity, divide by molar mass = 0.096/500 x 10.8 x 2/249.7 M
moles CuSO4.5H20=.096/250
moles transfered: 10.8/.500*.096/250
molarity second solultion:
10.8/.500*.096/250*1/.5
check that, it is not the same as your solution
To find the molarity of CuSO4 in the second solution, you need to follow these steps:
1. Calculate the mass of CuSO4 · 5 H2O dissolved in the 10.8 mL sample taken from the first solution.
- Use the given mass of CuSO4 · 5 H2O in the initial solution (0.096 g) and the total volume of the initial solution (500 mL) to calculate the mass per mL of the initial solution.
- Then, multiply the mass per mL by the volume of the sample taken (10.8 mL) to find the mass of CuSO4 · 5 H2O in the sample.
2. Determine the mass of CuSO4 · 5 H2O in the second solution.
- Since the sample was transferred to a second 500 mL volumetric flask and diluted, the mass per liter of CuSO4 · 5 H2O in the second solution is the same as the mass per liter in the first solution.
- Multiply the mass of CuSO4 · 5 H2O in the sample by 2 (to account for the dilution) to find the mass per liter in the second solution.
3. Calculate the molarity of CuSO4 in the second solution.
- Divide the mass per liter of CuSO4 · 5 H2O in the second solution by the molar mass of CuSO4 (249.7 g/mol) to find the molarity of CuSO4 in the second solution.
So, to summarize:
1. Calculate the mass of CuSO4 · 5 H2O in the sample:
- Mass of CuSO4 per mL = (0.096 g) / (500 mL)
- Mass of CuSO4 in 10.8 mL sample = (Mass of CuSO4 per mL) x (10.8 mL)
2. Determine the mass of CuSO4 · 5 H2O in the second solution:
- Mass of CuSO4 · 5 H2O per liter in the second solution = (Mass of CuSO4 in 10.8 mL sample) x (2)
- Convert the mass to grams per liter.
3. Calculate the molarity of CuSO4 in the second solution:
- Molarity = (Mass of CuSO4.5H2O per liter) / (Molar mass of CuSO4)
Plug in the values you calculated and calculate the final molarity accordingly.