Respuesta :
Explanation:
The reaction equation will be as follows.
[tex]Mg(OH)_{2} + 2HCl \rightarrow MgCl_{2} + 2H_{2}O[/tex]
It is given that mass of magnesium hydroxide is 400 mg or 0.4 g (as 1 g = 1000 g). Molar mass of [tex]Mg(OH)_{2}[/tex] is 58.31 g/mol.
Therefore, calculate the number of moles of [tex]Mg(OH)_{2}[/tex] as follows.
No. of moles = [tex]\frac{mass}{\text{molar mass}}[/tex]
= [tex]\frac{0.4 g}{58.31 g/mol}[/tex]
= [tex]6.85 \times 10^{-3}[/tex] mol
= 0.00685 mol
Now, moles of HCl = 2 × moles of [tex]Mg(OH)_{2}[/tex]
= 2 × 0.00685 mol
= 0.0137 mol
Concentration of HCl = [tex]10^{-pH}[/tex] = [tex]10^{-1.4}[/tex] = 0.0398 M
Now, we will calculate the volume of HCl as follows.
Volume of HCl = [tex]\frac{moles}{\text{concentration of HCl}}[/tex]
= [tex]\frac{0.0137}{0.0398}[/tex]
= 0.344 L
or, = 344 ml (as 1 L = 1000 ml)
Thus, we can conclude that 344 ml of an HCl solution with a pH of 1.4 can be neutralized by one dose of milk of magnesia.
0.35 L of HCl at pH 1.4 is required to neutralize one dose of milk of magnesia.
We can obtain the concentration of hydrogen ions from the pH as follows;
pH = -log[H^+]
[H^+] =Antilog(-pH)
[H^+] = Antilog (-1.4)
[H^+] = 0.0398 M
Now, the reaction equation is;
Mg(OH)2 + 2HCl -----> MgCl2 + 2H2O
Mass of Mg(OH)2 reacted = 4.00×10²mg or 0.4 g
Number of moles of Mg(OH)2 = 0.4 g/58 g/mol = 0.00689 moles
If 1 mole of Mg(OH)2 reacts with 2 moles of HCl
0.00689 moles of Mg(OH)2 reacts with 0.00689 moles × 2 moles/1 mole
= 0.0138 moles of HCl
Note that;
Number of moles = concentration × volume
Volume = Number of moles/concentration
Volume = 0.0138 moles/0.0398 M
Volume = 0.35 L
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