If 1.0 g of hydrogen reacts completely with 19.0 g of fluoride. What is the mass of the compound formed? What is the percent by mass of hydrogen in the compound formed?
Answers
Mass of hydrogen = 1 g
Mass of fluorine = 19 g
Molar mass of hydrogen = 2 g/mole
Molar mass of fluorine = 38 g/mole
First we have to calculate the moles of hydrogen and fluorine.
\text{Moles of }H_2=\frac{\text{Mass of }H_2}{\text{Molar mass of }H_2}=\frac{1g}{2g/mole}=0.5molesMoles of H
2
=
Molar mass of H
2
Mass of H
2
=
2g/mole
1g
=0.5moles
\text{Moles of }F_2=\frac{\text{Mass of }F_2}{\text{Molar mass of }F_2}=\frac{19g}{38g/mole}=0.5molesMoles of F
2
=
Molar mass of F
2
Mass of F
2
=
38g/mole
19g
=0.5moles
Now we have to calculate the moles of HF.
The balanced chemical reaction is,
H_2+F_2arrow 2HFH
2
+F
2
arrow2HF
From the balanced reaction we conclude that
As, 1 mole of H_2H
2
react to give 2 moles of HFHF
So, 0.5 mole of H_2H
2
react to give 0.5\times 2=10.5×2=1 moles of HFHF
Now we have to calculate the percent by mass of hydrogen in the compound.
\text{Percent by mass of hydrogen}=\frac{\text{Mass of hydrogen}}{\text{Total mass of compound}}\times 100=\frac{1}{1+19}\times 100=5\%Percent by mass of hydrogen=
Total mass of compound
Mass of hydrogen
×100=
1+19
1
×100=5%
Therefore, the mass of hydrogen in the compound that is formed are, 5 %
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