Question

Chemistry

How many grams of CaCl2 are in 250 mL of 2.0 M CaCl2?

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Best Answer

The answer is: "

2.0 M CaCl₂ = 2.0 mol CaCl₂ / L ;

Since: "M" = "Molarity" (measurement of concentration);

= moles of solute per L {"Liter"} of solution.

Note the exact conversion: 1000 mL = 1 L .

Given: 250 mL ;

250 mL = ? L ? ;

250 mL * (1 L / 1000 L) = (250/1000) L = 0.25 L .

(2.0 mol CaCl₂ / L ) * (0.25L) = (2.0) * (0.25) mol = 0.50 mol CaCl₂ ;

We have: 0.50 mol CaCl₂ ; Convert to "g" (grams):

→ 0.50 mol CaCl₂ .

1 mol CaCl₂ = ? g ?

From the Periodic Table of Elements:

1 mol Ca = 40.08 g

1 mol Cl = 35.45 g .

There are 2 atoms of Cl in " CaCl

→ Note the subscript, "2", in the " Cl₂ " ;

So, to calculate the molar mass of "CaCl₂" :

40.08 g + 2(35.45 g) =

40.08 g + 70.90 g = 110.98 g ; round to 4 significant figures;

→ round to 111 g/mol .

So:

→ 0.50 mol CaCl₂ = ? g CaCl₂ ? ;

→ 0.50 mol CaCl₂ * (111 g CaCl₂ / mol CaCl₂) ;

= (0.50) * (111 g) CaCl₂ ;

= 55.5 g CaCl₂ ;

→ round to 2 significant figures;

→

**56 g CaCl₂**" .**__________________________________________________________****Explanation:****__________________________________________________________**2.0 M CaCl₂ = 2.0 mol CaCl₂ / L ;

Since: "M" = "Molarity" (measurement of concentration);

= moles of solute per L {"Liter"} of solution.

**__________________________________________________________**Note the exact conversion: 1000 mL = 1 L .

Given: 250 mL ;

250 mL = ? L ? ;

250 mL * (1 L / 1000 L) = (250/1000) L = 0.25 L .

**___________________________________________________________**(2.0 mol CaCl₂ / L ) * (0.25L) = (2.0) * (0.25) mol = 0.50 mol CaCl₂ ;

We have: 0.50 mol CaCl₂ ; Convert to "g" (grams):

→ 0.50 mol CaCl₂ .

**___________________________________________________________**1 mol CaCl₂ = ? g ?

From the Periodic Table of Elements:

1 mol Ca = 40.08 g

1 mol Cl = 35.45 g .

There are 2 atoms of Cl in " CaCl

**₂**" ;→ Note the subscript, "2", in the " Cl₂ " ;

**__________________________________________________________**So, to calculate the molar mass of "CaCl₂" :

40.08 g + 2(35.45 g) =

40.08 g + 70.90 g = 110.98 g ; round to 4 significant figures;

→ round to 111 g/mol .

**__________________________________________________________**So:

→ 0.50 mol CaCl₂ = ? g CaCl₂ ? ;

→ 0.50 mol CaCl₂ * (111 g CaCl₂ / mol CaCl₂) ;

= (0.50) * (111 g) CaCl₂ ;

= 55.5 g CaCl₂ ;

→ round to 2 significant figures;

→

**56 g CaCl₂**.**___________________________________________________________****The answer is:**"**56 g CaCl₂**" .**___________________________________________________________**