Answer:
Molarity or molar concentration is the number of moles of solute that can be dissolved in 1 L of a solution.
Molarity = Number of solute (in moles) / Volume of solution (in liters), or
C = n / V
According to the question,
V = 750 ml and C = 0.100 M
For this, let us convert ml into liters
We know 1 L = 1000 ml
Hence, 750 ml = (750/1000) L = 0.75 L
So, V = 0.75 L
We know that C = n / V
So, n = C x V
n = 0.100 x 0.75 = 0.075
n is the number of moles of solute.
Hence, number of moles of CaCl2 = 0.075 moles
That means there are 0.075 moles of CaCl2 in 750 ml of solution.
In order to determine the mass of CaCl2 in grams, we need to know the molar mass of CaCl2.
For this, we need to find out the atomic mass of each atom (by referring the periodic table).
CaCl2 has 1 Ca atom and 2 Cl atoms.
Atomic mass of
Ca = 40.08 g
Cl = 35.45, Cl2 means 2 x 35.45 = 70.90 g
Adding these values, we get mass of CaCl2 in grams.
Hence, mass of CaCl2 = 40.08 + 70.90 = 110.98 g
Thus, 1 mole of CaCl2 weighs 110.98 g.
Hence, 0.075 moles of CaCl2 will weigh
0.075 x 110.98 = 8.3235 g, rounded to 8.32 g
So restating the question, we can say that 8.32 grams of CaCl2 will be needed to make 750 ml of a 0.100 M CaCl2 solution.
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