The following data is for the solubility of lead (II) bromide in water.
0 C: 0.455 g per 100 ml solution
20 C: 0.844 g per 100 ml solution
100 C: 4.71 g per 100 ml solution
A) What is the concentration of lead(II)bromide in moles per liter in each of these saturated solutions?
B) Using the values from part a, calculate the solubility product constants for lead (II) bromide at 0, 20, and 100 C.
C) What do the solubilities given in part a imply about the sign ΔH for the dissolving of lead(II) bromide? Explain.
0 C: 0.455 g per 100 ml solution
20 C: 0.844 g per 100 ml solution
100 C: 4.71 g per 100 ml solution
A) What is the concentration of lead(II)bromide in moles per liter in each of these saturated solutions?
B) Using the values from part a, calculate the solubility product constants for lead (II) bromide at 0, 20, and 100 C.
C) What do the solubilities given in part a imply about the sign ΔH for the dissolving of lead(II) bromide? Explain.
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The following data is for the solubility of lead (II) bromide in water.
0 C: 0.455 g per 100 ml solution
20 C: 0.844 g per 100 ml solution
100 C: 4.71 g per 100 ml solution
A) What is the concentration of lead(II)bromide in moles per liter in each of these saturated solutions?
mass of 1 mole of Pb(Br)2 = 207.2 + 2 * 79.9 = 367 g
(0.454 ÷ 367) moles ÷ 0.1 L = 0.01237
(0.844 ÷ 367) moles ÷ 0.1 L =
(4.71 ÷ 367) moles ÷ 0.1 L =
B) Using the values from part a, calculate the solubility product constants for lead (II) bromide at 0, 20, and 100 C.
Solubility product = [Pb+2] * [Br-1]^2
Since each mole of Pb(Br)2 contains 1 mole of Pb+2 ions and 2 moles of Br-1 ion, [Br-1] = 2 * [Pb+2]
Solubility product at 0° = (0.01237) * (0.01237)^2
C) What do the solubilities given in part a imply about the sign ΔH for the dissolving of lead(II) bromide? Explain.
Pb(Br)2 + H2O → solution + heat
or
Pb(Br)2 + H2O + heat → solution
The solubility increases as the temperature increases, heat must be released.
http://en.wikipedia.org/wiki/Enthalpy
The change ΔH is positive in endothermic reactions, and negative in exothermic processes
The solubility of a solute decreases as the temperature increases, when the heat of solution is negative.
The solubility of a solute increases as the temperature increases, when the heat of solution is positive.
Increasing the temperature of this substance caused the solubility to increase. Increasing the temperature means you are adding heat energy to the solution. This means the solution is absorbing heat energy as the solution process occurs.
Absorbing heat energy is endothermic, and endothermic means ΔH is positive!
0 C: 0.455 g per 100 ml solution
20 C: 0.844 g per 100 ml solution
100 C: 4.71 g per 100 ml solution
A) What is the concentration of lead(II)bromide in moles per liter in each of these saturated solutions?
mass of 1 mole of Pb(Br)2 = 207.2 + 2 * 79.9 = 367 g
(0.454 ÷ 367) moles ÷ 0.1 L = 0.01237
(0.844 ÷ 367) moles ÷ 0.1 L =
(4.71 ÷ 367) moles ÷ 0.1 L =
B) Using the values from part a, calculate the solubility product constants for lead (II) bromide at 0, 20, and 100 C.
Solubility product = [Pb+2] * [Br-1]^2
Since each mole of Pb(Br)2 contains 1 mole of Pb+2 ions and 2 moles of Br-1 ion, [Br-1] = 2 * [Pb+2]
Solubility product at 0° = (0.01237) * (0.01237)^2
C) What do the solubilities given in part a imply about the sign ΔH for the dissolving of lead(II) bromide? Explain.
Pb(Br)2 + H2O → solution + heat
or
Pb(Br)2 + H2O + heat → solution
The solubility increases as the temperature increases, heat must be released.
http://en.wikipedia.org/wiki/Enthalpy
The change ΔH is positive in endothermic reactions, and negative in exothermic processes
The solubility of a solute decreases as the temperature increases, when the heat of solution is negative.
The solubility of a solute increases as the temperature increases, when the heat of solution is positive.
Increasing the temperature of this substance caused the solubility to increase. Increasing the temperature means you are adding heat energy to the solution. This means the solution is absorbing heat energy as the solution process occurs.
Absorbing heat energy is endothermic, and endothermic means ΔH is positive!