how many grams of water must be added to 75.5 grams of Ca(NO3)2 to for a 0.500 m solution
m as in molality? Normally this question is Molarity.
molality= molesSolute/kg of water
.5= moles/1000*grams water
gramswater= 75.5g/(molmass*1000*.5)
solve for grams water.
To calculate how many grams of water must be added to 75.5 grams of Ca(NO3)2 to form a 0.500 m (molality) solution, we need to use the formula:
m = moles of solute / mass of solvent (kg)
First, we need to convert the given mass of Ca(NO3)2 to moles.
The molar mass of Ca(NO3)2 is:
Ca: 40.08 g/mol
N: 14.01 g/mol
O: 16.00 g/mol
So, the molar mass of Ca(NO3)2 is:
40.08 g/mol + (14.01 g/mol x 2) + (16.00 g/mol x 6) = 164.09 g/mol
Using the molar mass, we can calculate the number of moles of Ca(NO3)2:
moles = mass / molar mass
moles = 75.5 g / 164.09 g/mol
Next, we need to convert the molality (m) to moles of solute per kilogram of solvent.
0.500 m = moles of solute / mass of solvent (kg)
We can rearrange this equation to solve for moles of solute:
moles of solute = 0.500 m x mass of solvent (kg)
Finally, we can solve for the mass of solvent (water):
mass of solvent (kg) = moles of solute / 0.500 m
To convert the mass of solvent to grams, we multiply by 1000:
mass of water (grams) = mass of solvent (kg) x 1000
Therefore, the number of grams of water needed to be added to 75.5 grams of Ca(NO3)2 to form a 0.500 m solution is given by the equation:
mass of water (grams) = (moles of Ca(NO3)2 / 0.500 m) x 1000
To find out how many grams of water must be added to 75.5 grams of Ca(NO3)2 to form a 0.500 M solution, we first need to understand the concept of molarity and then apply the appropriate formula to solve the problem.
Molarity (M) is a measure of concentration, defined as the number of moles of solute dissolved in one liter of solution. By definition, 1 mole of any substance is equal to its molecular weight in grams.
Given the molarity (0.500 M) and the amount of Ca(NO3)2 (in grams), we can calculate the number of moles of Ca(NO3)2 in the given amount as follows:
Number of moles of Ca(NO3)2 = Mass of Ca(NO3)2 / Molecular weight of Ca(NO3)2
The molecular weight of Ca(NO3)2 can be determined by adding up the atomic masses of its constituent elements:
1 atom of Ca: 1 * atomic mass of Ca
2 atoms of N: 2 * atomic mass of N
6 atoms of O: 6 * atomic mass of O
Now, divide the mass of Ca(NO3)2 (75.5 grams) by the calculated molecular weight to get the number of moles.
Next, we need to determine the number of moles of water present in the solution. Since water (H2O) is the solvent in this case, we assume its mass to be equivalent to the mass of the solution for simplicity.
Finally, we subtract the mass of Ca(NO3)2 from the total mass of the solution to find the mass of water required. This ensures that the final solution has the desired molarity.
So, to summarize the steps to calculate the mass of water required:
1. Determine the molecular weight of Ca(NO3)2.
2. Calculate the number of moles of Ca(NO3)2 by dividing its mass by its molecular weight.
3. Assume the mass of water to be equal to the mass of the solution.
4. Subtract the mass of Ca(NO3)2 from the total mass of the solution to find the mass of water required.
Once you have followed these steps, you will have the mass of water needed to form a 0.500 M solution with 75.5 grams of Ca(NO3)2.