Equilibrium Constant Calculations - Video Tutorials & Practice Problems
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concept
Equilibrium Constant Calculations
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Here, we can say that when all equilibrium concentrations of reaction are known, then our equilibrium constant K can be calculated. In addition to this, we can also say that your equilibrium constant can also be used to calculate one missing equilibrium concentration. If we take a look here at this example question it says what is the value of the equilibrium constant KC for the reaction below? If the equilibrium mixture contains 0.255 molar of methane, 1.10 molar of carbon dioxide, 0.388 molar of carbon monoxide and 0.250 molar of hydrogen gas. Now, here they're telling us this is an equilibrium mixture. So these are all equilibrium concentrations. We say that K equals products over reactants. Remember we exclude solids and liquids from this expression. Since everything is a gas, everything is going to be included, we're gonna have here products overreacted. So that's co since it's coefficient is a two, that's gonna be squared times H two coefficient is two. So that's also squared divided by methane which has a coefficient of one. So we don't need to include it times the concentration of CO2. Now we're going to plug in the values given to us for each of the compounds. We have carbon monoxide as being 0.388 molar, which is going to be squared times 0.250 molar for H two, which is also squared divided by here, we have 0.255 molar for methane. And we have 1.10 molar for carbon dioxide. We plug this into our calculators and what we will get initially, I'm gonna give a long string of numbers and then we're gonna um round it down. So we're gonna say here we have 0.033543672 our equilibrium constant K has no units. So we're not gonna plug in molarity or anything. It's just this value here. We're gonna say within our question, all the values given to us have three significant figures. So we're gonna give K three significant figures. This means that our final answer is going to be 0.0335. This represents the answer for equilibrium constant K from the given example question.
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Problem
Problem
The reaction: 2 NO(g) + Br2(g) ⇌ 2 NOBr(g), has a Kp of 2.5 x 102 at 35°C. Calculate the equilibrium concentration of NOBr, if equilibrium concentrations of NO and Br2 are 0.2 atm and 0.050 atm, respectively.
A
2 atm
B
0.7 atm
C
1 atm
D
0.5 atm
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Problem
Problem
For the reaction below, Kc = 1.5 at a constant temperature. A 3.2 L flask contains an equilibrium mixture of 3 compounds: 3.7 g of NH4HS, 70. g of NH3 and unknown amount of H2S. What is the mass (grams) of H2S produced at equilibrium?
NH4HS(s) ⇌ NH3(g) + H2S(g)
A
12.4 g H2S
B
433 g H2S
C
130 g H2S
D
210 g H2S
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