Answer to Question #194498 in Chemistry for Jamel

Question

A 0.674\,\text M

0.674M

0, point, 674, start text, M, end text

 cobalt(II) chloride (\text{CoCl}_2

CoCl2

​

start text, C, o, C, l, end text, start subscript, 2, end subscript

) solution is prepared with a total volume of 0.0750\,\text{L}

0.0750L

0, point, 0750, start text, L, end text

. The molecular weight of \text{CoCl}_2

CoCl2

​

start text, C, o, C, l, end text, start subscript, 2, end subscript

 is 128.9\,\dfrac{\text{g}}{\text{mol}}

128.9mol

g

​

128, point, 9, start fraction, start text, g, end text, divided by, start text, m, o, l, end text, end fraction

.

What mass of \text{CoCl}_2

CoCl2

​

start text, C, o, C, l, end text, start subscript, 2, end subscript

 (in grams) is needed for the solution?

Express the answer using 3 significant figures.

Answer 1

A 0.674 M cobalt(II) chloride (CoCl₂) solution is prepared with a total volume of 0.0750 L. The molecular weight of CoCl₂ is 128.9 g/mol. What mass of CoCl₂ (in grams) is needed for the solution?

Express the answer using 3 significant figures.

Solution:

Molarity of CoCl₂ solution = Moles of CoCl₂ / Solution volume

Moles of CoCl₂ = Mass of CoCl₂ / Molecular weight of CoCl₂

Molarity of CoCl₂ solution = Mass of CoCl₂ / (Molecular weight of CoCl₂ × Solution volume)

Therefore,

Mass of CoCl₂ = Molarity of CoCl₂ solution × Molecular weight of CoCl₂ × Solution volume

Mass of CoCl₂ = (0.674 mol L^-1) × (128.9 g mol^-1) × (0.0750 L) = 6.5159 g = 6.52 g

Mass of CoCl₂ = 6.52 g

Answer: 6.52 grams of CoCl₂ is needed for the solution.