A student is given 0.325 g of CaCl2 and is instructed to make 25.0 ml of 0.100-mol/L CaCl2 using all of the solid. The following materials are provided:
To make 25.0 ml of 0.100-mol/L CaCl2, the student is given 0.325 g of CaCl2. The following materials are provided:
- 0.325 g of CaCl2
- Deionized water
- A 25.0 ml volumetric flask
The student needs to dissolve the entire 0.325 g of CaCl2 in enough deionized water to make a final volume of 25.0 ml.
To calculate the amount of CaCl2 needed to make 25.0 mL of a 0.100-mol/L solution, we need to first convert the volume of the solution to liters.
Given:
- Mass of CaCl2 = 0.325 g
- Desired concentration = 0.100 mol/L
- Volume of solution = 25.0 mL
First, convert the volume of the solution to liters:
25.0 mL = 25.0 mL / 1000 mL/L = 0.0250 L
To find the amount of CaCl2 needed, we use the formula:
Amount of substance (in moles) = Concentration (in mol/L) × Volume (in L)
Plugging in the values we have:
Amount of substance (in moles) = 0.100 mol/L × 0.0250 L
= 0.0025 mol
Next, we need to find the molar mass of CaCl2. The molar mass of calcium (Ca) is 40.08 g/mol, and the molar mass of chlorine (Cl) is 35.45 g/mol. Since there are two chlorine atoms in CaCl2, we multiply the molar mass of chlorine by 2.
Molar mass of CaCl2 = (40.08 g/mol) + (2 × 35.45 g/mol)
= 40.08 g/mol + 70.90 g/mol
= 110.98 g/mol
Finally, calculate the mass of CaCl2 needed using the formula:
Mass = Amount of substance (in moles) × Molar mass
Mass = 0.0025 mol × 110.98 g/mol
= 0.2775 g
Therefore, the student needs 0.2775 g of CaCl2 to make 25.0 mL of a 0.100-mol/L solution.
To solve this problem, we need to determine the volume of water required to dissolve 0.325 g of CaCl2 to create a 0.100-mol/L solution.
First, we need to find the number of moles of CaCl2 present in 0.325 g. We will use the molar mass of CaCl2 to convert grams to moles.
The molar mass of CaCl2 is:
Ca: 40.08 g/mol
Cl: 2 * 35.45 g/mol = 70.90 g/mol
Therefore, the molar mass of CaCl2 is:
40.08 g/mol + 70.90 g/mol = 111.98 g/mol
To find the number of moles, we use the formula:
moles = mass / molar mass
moles = 0.325 g / 111.98 g/mol
moles = 0.002904 mol
Now, we can use the molarity formula to find the volume of water required. The formula is:
moles = concentration (mol/L) * volume (L)
We know that the concentration (C) is 0.100 mol/L and the number of moles (n) is 0.002904 mol. Rearranging the formula, we get:
volume (L) = moles / concentration (mol/L)
volume (L) = 0.002904 mol / 0.100 mol/L
volume (L) = 0.02904 L = 29.04 mL
Therefore, to make a 0.100-mol/L CaCl2 solution using 0.325 g of CaCl2, you will need to dissolve the solid in approximately 29.04 mL of water.