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How much CaF2 (in grams) is formed when 15.7 mL of 0.612 M KF reacts with an excess of aqueous calcium bicarbonate?

Respuesta :

0.375 g of [tex]CaF_2[/tex] will be produced from the given masses of both reactants.

Explanation:

To calculate the number of moles for given molarity, we use the equation:

[tex]\text{Molarity of the solution}=\frac{\text{Moles of solute}\times 1000}{\text{Volume of solution (in L)}}[/tex]     .....(1)

Molarity of [tex]KF[/tex] solution = 0.612 M

Volume of [tex]KF[/tex] solution = 15.7 mL

Putting values in equation 1, we get:

[tex]0.612M=\frac{\text{Moles of KF}\times 1000}{15.7ml}\\\\\text{Moles of KF}=\frac{0.612mol/L\times 15.7}{1000}=9.61\times 10^{-3}mol[/tex]

The balanced chemical reaction is:

[tex]2KF+Ca(HCO_3)_2\rightarrow CaF_2+2KHCO_3[/tex]

As [tex]KF[/tex] is the limiting reagent as it limits the formation of product and [tex]Ca(HCO_3)_2[/tex] is the excess reagent.

According to stoichiometry :

2 moles of [tex]KF[/tex] give =  1 mole of [tex]CaF_2[/tex]

Thus [tex]9.61\times 10^{-3}mol[/tex]  moles of [tex]KF[/tex] will require=[tex]\frac{1}{2}\times 9.61\times 10^{-3}mol=4.80\times 10^{-3}mol[/tex] of [tex]CaF_2[/tex]

Mass of [tex]CaF_2=moles\times {\text {Molar mass}}=4.80\times 10^{-3}moles\times 78.07g/mol=0.375g[/tex]

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