Answer: 0.1161 grams of mercury(II) sulfide) form.
Explanation:
To calculate the number of moles for given molarity, we use the equation:
.....(1)
a) Molarity of
solution = 0.10 M
Volume of solution = 0.020 L
Putting values in equation 1, we get:
![0.10M=\frac{\text{Moles of }Na_2S}{0.020L}\\\\\text{Moles of Na_2S}={0.10mol/L\times 0.020}=0.002mol](https://tex.z-dn.net/?f=0.10M%3D%5Cfrac%7B%5Ctext%7BMoles%20of%20%7DNa_2S%7D%7B0.020L%7D%5C%5C%5C%5C%5Ctext%7BMoles%20of%20Na_2S%7D%3D%7B0.10mol%2FL%5Ctimes%200.020%7D%3D0.002mol)
![\text {Moles of}Na_2S=0.10M\times 0.020L=0.002mol](https://tex.z-dn.net/?f=%5Ctext%20%7BMoles%20of%7DNa_2S%3D0.10M%5Ctimes%200.020L%3D0.002mol)
b) Molarity of
solution = 0.010 M
Volume of solution = 0.050 L
Putting values in equation 1, we get:
![0.010M=\frac{\text{Moles of }Hg(NO_3)_2}{0.050L}\\\\\text{Moles of }Hg(NO_3)_2={0.010mol/L\times 0.050}=0.0005mol](https://tex.z-dn.net/?f=0.010M%3D%5Cfrac%7B%5Ctext%7BMoles%20of%20%7DHg%28NO_3%29_2%7D%7B0.050L%7D%5C%5C%5C%5C%5Ctext%7BMoles%20of%20%7DHg%28NO_3%29_2%3D%7B0.010mol%2FL%5Ctimes%200.050%7D%3D0.0005mol)
![Na_2S+Hg(NO_3)_2\rightarrow HgS+2NaNO_3](https://tex.z-dn.net/?f=Na_2S%2BHg%28NO_3%29_2%5Crightarrow%20HgS%2B2NaNO_3)
According to stoichiometry :
1 mole of
reacts with 1 mole of ![Na_2S](https://tex.z-dn.net/?f=Na_2S)
Thus 0.0005 moles of
reacts with=
moles of ![Hg(NO_3)_2](https://tex.z-dn.net/?f=Hg%28NO_3%29_2)
Thus
is the limiting reagent and
is the excess reagent.
According to stoichiometry :
1 mole of
forms= 1 mole of ![Hg_2S](https://tex.z-dn.net/?f=Hg_2S)
Thus 0.0005 moles of
forms=
moles of ![Hg_2S](https://tex.z-dn.net/?f=Hg_2S)
mass of ![H_2S=moles\times {\text {Molar mass}}=0.0005mol\times 232.2g/mol=0.1161g](https://tex.z-dn.net/?f=H_2S%3Dmoles%5Ctimes%20%7B%5Ctext%20%7BMolar%20mass%7D%7D%3D0.0005mol%5Ctimes%20232.2g%2Fmol%3D0.1161g)
Thus 0.1161 grams of mercury(II) sulfide) form.