Assignment 5
Example 1
If 500 mL of HCl gas at 300 K and 100 kPa dissolve in 100 mL of pure water, what is the concentration? Data required:Rvalue 8.314 kPa L / (K mol).
Solution:
0.50 L * 100 kPa
n_HCl = ------
(8.314 kPa L/(K mol) * 300 K)
= 0.02 mol
Concentration of HCl, [HCl]
[HCl] = 0.02 mol / 0.1 L = 0.2 mol/L.
Discussion
Note thatR= 0.08205 L atm/(K mol) will not be suitable in this case.
Example 2
If 500 mL of HCl gas at 300 K and 100 kPa dissolved in pure water requires 12.50 mL of the NaOH solution to neutralize in a titration experiment, what is the concentration of the NaOH solution?
Solution:
Solution in Example 1 showednHCl= 0.02 mol. From the titration experiment, we can conclude that there were 0.02 moles of NaOH in 12.50 mL. Thus,
[NaOH] = 0.02 mol / 0.0125 L = 1.60 mol/L
Discussion:
Think in terms of reaction,
HCl + NaOH = NaCl + H2O <== Reaction
0.02 mol 0.02 mol <== Quantities reacted
Note: that 0.02 mol of NaOH is in 0.0125 mL solution.
Example 3:
A 5.0-L air sample containing H2S at STP is treated with a catalyst to promote the reaction,
H2S + O2= H2O + S(solid).
If 3.2 g of solid S was collected, calculate the volume percentage of H2S in the origional sample.
Solution:
1 mol H2S
3.2 g S ------= 0.10 mol H2S
32 g S
V_H2S = 0.10 mol * 22.4 L/mol
= 2.24 L
Volume % = 2.25 L / 5.0 L
= 0.45
= 45 %
Discussion:
Data required: Atomic mass: H, 1; O, 16; S, 32.R= 0.08205 L atm/(K mol) is now suitableRvalues or molar volume at STP (22.4 L/mol)
The volume percentage is also the mole percentage, but not the weight percentage.
Example 4:
Hydrogen sulfide reacts with sulfur dioxide to give H2O and S,
H2S + SO2= H2O + S(solid), unbalanced.
If 6.0 L of H2S gas at 750 torr produced 3.2 g of sulfur, calculate the temperature in C.
Solution
Balanced reaction:
2 H2S + SO2 = 2 H2O + 3 S(solid),
2 mol 3*32 = 96 g
2 mol H2S
3.2 g S ------= 0.067 mol H2S;
96 g S
P = 750/760 = 0.987 atm
PV 0.987 atm * 6 L
T = --- = ------
n R 0.067 mol * 0.08205 atm L /(mol K)
= 1085 K
= 812°C
Discussion:
Atomic mass: H, 1.0; O, 16.0; S, 32.0.R= 0.08205 L atm/(K mol) is OK but watch units used for pressure.
Example 6:
What volume (L) will 0.20 mol HI occupy at 300 K and 100.0 kPa?R= 8.314 kPa L / (K mol) = 0.08205 atm L / (mol K).
Solution
n RT
V = ----
P
0.20 mol * 8.314 kPa L / (mol K) *300 K
= ------
100 kPa
= 5 L,
Advanced Stoichiometry
Confidence Building Questions
Top of Form
If 100 mL of HCl gas at 300 K and 100 kPa dissolve in 20 mL of pure water, what is the concentration?
Skill:
Calculatenusing ideal gas law.
Bottom of Form
- If 100 mL of HCl gas at 300 K and 100 kPa dissolved in pure water requires 12.50 mL of the NaOH solution to neutralize in a titration experiment, what is the concentration of the NaOH solution?
Top of Form
Skill:
Apply ideal gas law to solve stoichiometry problems.
Bottom of Form
Top of Form
If 100 mL of HCl gas at 300 K and 200 kPa dissolved in pure water requires 12.50 mL of the NaOH solution to neutralize in a titration experiment, what is the concentration of the NaOH solution?
Skill:
Solve stoichiometric problem.
Bottom of Form
Top of Form
Hydrogen sulfide reacts with sulfur dioxide to give H2O and S,
H2S + SO2= H2O + S(solid), unbalanced.
If 3.0 L of H2S gas at 760 torr produced 4.8 g of sulfur, calculate the temperature in C.
Skill:
Apply ideal gas law to solve stoichiometry problems.
Bottom of Form
Top of Form
When 10.0 mL of AgNO3solution is treated with excess amount of HI gas to give 0.235 g of AgI, calculate the concentration of AgNO3solution.
Bottom of Form
Top of Form
When an AgNO3solution is treated with 50.0 mL of HI gas to give 0.235 g of AgI, calculate the concentration of HI gas.
Bottom of Form
Top of Form
When an AgNO3solution is treated with 50.0 mL of HI gas at 300 K to give 0.235 g of AgI, calculate the pressure of the HI gas.
Discussion:
Depending on the numerical values you use, you may get the pressure in other units.
Bottom of Form
Top of Form
When an AgNO3solution is treated with 50.0 mL of HI gas at 374 torr to give 0.235 g of AgI, calculate the temperature of the HI gas.
Discussion:
Note the relationship of this problem with the previous one.
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