A solution is 25% by mass calcium nitrate and has a density of 1.21 g/mL what is the molarity?
We can help you better if you don't change screen names. Work this problem just backwards from the NaOH problem above.
To find the molarity of the solution, we first need to calculate the mass of calcium nitrate in the solution. Since the solution is 25% by mass calcium nitrate, we know that 25 g of the solution contains 25% of calcium nitrate.
Since we don't know the volume of the solution, we can assume a desired volume to simplify the calculation. Let's assume we have 100 mL of the solution, which is equal to 100 g since the density is 1.21 g/mL.
Now, we can calculate the mass of calcium nitrate in the assumed 100 g of the solution by multiplying the mass of the solution (100 g) by the percentage of calcium nitrate (25%):
Mass of calcium nitrate = 100 g x 25% = 25 g
Next, we need to convert the mass of calcium nitrate to moles. To do this, we divide the mass of calcium nitrate by its molar mass. Calcium nitrate has a formula of Ca(NO3)2, and its molar mass is calculated as follows:
(1 atom of Ca x atomic mass of Ca) + (2 groups of NO3 x molar mass of NO3)
= (1 x 40.08 g/mol) + (2 x (1 x 14.01 g/mol + 3 x 16.00 g/mol))
= 164.09 g/mol
Now, we can calculate the number of moles of calcium nitrate:
Moles of calcium nitrate = Mass of calcium nitrate / Molar mass of calcium nitrate
= 25 g / 164.09 g/mol ≈ 0.152 moles
Finally, to find the molarity of the solution, we divide the number of moles of calcium nitrate by the volume of the solution in liters (100 mL = 0.1 L):
Molarity = Moles of calcium nitrate / Volume of solution (in L)
= 0.152 moles / 0.1 L ≈ 1.52 M
Therefore, the molarity of the solution is approximately 1.52 M.