Respuesta :
The mass of LiOH needed to make a 300 mL of a solution with a pH of 11.33 is 0.015 g
We'll begin by calculating the pOH of the solution.
pH = 11.33
pOH =?
pH + pOH = 14
11.33 + pOH = 14
Collect like terms
pOH = 14 – 11.33
pOH = 2.67
- Next, we shall determine the concentration of hydroxide ion, OH⁻
pOH = 2.67
Concentration of hydroxide ion [OH⁻] = ?
pOH = –Log [OH⁻]
2.67 = –Log [OH⁻]
–2.67 = Log [OH⁻]
Take the as antilog of –2.67
[OH⁻] = antilog (–2.67)
[OH⁻] = 0.0021 M
- Next, we shall determine the concentration of LiOH.
LiOH(aq) —> Li⁺(aq) + OH⁻(aq)
From the balanced equation above,
1 mole of LiOH contains 1 mole of OH⁻
Therefore,
0.0021 M LiOH will also contain 0.0021 M OH⁻.
- Next, we shall determine the mole of LiOH in the solution.
Molarity of LiOH = 0.0021 M
Volume = 300 mL = 300 / 1000 = 0.3 L
Mole of LiOH =?
Mole = Molarity × volume
Mole of LiOH = 0.0021 × 0.3
Mole of LiOH = 0.00063 mole
- Finally, we shall determine the mass of LiOH needed to prepare the solution.
Mole of LiOH = 0.00063 mole
Molar mass of LiOH = 7 + 16 + 1 = 24 g/mol
Mass of LiOH = ?
Mass = mole × molar mass
Mass of LiOH = 0.00063 × 24
Mass of LiOH = 0.015 g
Therefore, the mass of LiOH needed to prepare the solution is 0.015 g
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