how many grams of beryllium chloride would you need to add to 125 ml of water to make a .050 molal solution
.50ml BeCl2
To calculate the number of grams of beryllium chloride needed to make a 0.050 molal solution in 125 ml of water, we need to follow these steps:
Step 1: Determine the molar mass of beryllium chloride.
Beryllium chloride (BeCl2) consists of one beryllium atom with a molar mass of approximately 9.01 g/mol and two chlorine atoms with a molar mass of approximately 35.45 g/mol each. Therefore, the molar mass of beryllium chloride (BeCl2) can be calculated as follows:
Molar mass = (1 * 9.01 g/mol) + (2 * 35.45 g/mol) = 9.01 g/mol + 70.90 g/mol = 79.91 g/mol.
Step 2: Calculate the moles of beryllium chloride needed.
A 0.050 molal solution means that there are 0.050 moles of beryllium chloride dissolved in 1,000 grams of water. So, to find the moles of beryllium chloride needed for 125 ml of water, we can use the following formula:
Moles of solute = molality * kg of solvent.
molality = 0.050 mol/kg (given)
kg of solvent = 125 ml * (1 g/ml) / 1,000 = 0.125 kg.
Now we can calculate the moles of beryllium chloride needed:
Moles of solute = 0.050 mol/kg * 0.125 kg = 0.00625 moles.
Step 3: Convert moles to grams.
To convert moles to grams, we can use the molar mass of beryllium chloride calculated in Step 1:
Mass = moles of solute * molar mass = 0.00625 moles * 79.91 g/mol ≈ 0.4994 g.
Therefore, approximately 0.4994 grams of beryllium chloride would be needed to make a 0.050 molal solution in 125 ml of water.