How many grams of calcium chloride will be needed to make 750 mL of a 0.100 M CaCl2 solution?

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.

when 25.0 ml of 0.700 mol/l naoh was mixed in a calorimeter with 25.0 ml of 0.700 mol/l hcl, both initially at 20.0 °c, the temperature increased to 22.1 °c. the heat capacity of the calorimeter is 279 j/°c.

the equation for the reaction is:

naoh + hcl → nacl + h₂o

moles of hcl = 0.0250 l hcl ×

0.700

mol hcl

1 l hcl = 0.0175 mol hcl

volume of solution = (25.0 + 25.0) ml = 50.0 ml

mass of solution = 50.0 ml soln ×

1.00

ml soln

= 50.0 g soln

δt=t2-t1

= (22.1 – 20.0) °c = 2.1 °c

the heats involved are

heat from neutralization + heat to warm solution + heat to warm calorimeter = 0

q1+q2+q3=0

nδh+mcδt+cδt=0

0.0175 mol ×

δh

+ 50.0 g × 4.184 j·g⁻¹°c⁻¹ × 2.1 °c + 279 j°c⁻¹ × 2.1 °c = 0

0.0175 mol ×

δh

+ 439.32 j + 585.9 j = 0

0.0175 mol ×

δh

= -1025.22 j

δh=1025.22j0.0175 mol= -58 600 j/mol = -58.6 kj/mol

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