I am super confused when it comes to these types of questions! Can someone check my work? None of my answers matched those of my teacher when she read them this morning for last night's homework. Please help!

1. Consider the following equilibrium reaction: 2PH3(g) <-> 2P(g) + 3H2(g)
Calculate Keq if it is found that there is 0.70 mols PH3, 0.49 mols P, and 1.2 mols H2 in a 3.0 mL flask.

My work: (1.2/3)^3 * (.49/3)^2/(.70/3>^2 = .03136 rounded .031
Is this right?
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2. When 250f of chlorine is introduced into an evacuated 1.00L flask, it is 25% dissociated into chlorine atoms. Write the reaction and calculate the equilibrium constant. Does the reaction favor reactants or products?

My work:
The reaction is Cl2 <-> 2Cl right?

Then convert grams to moles so 250g/34g = 7.35 moles Cl2

Then the ice chart would be:
For Cl2, I is 7.35, C = 1.84, and E is 5.51
For Cl, I is 0, C is 3.68, and E is 3.68

So the Keq would be (3.68^2)/5.51=2.46
Therefore, it favors products because it is over 1. Is this right?
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3. The equilibrium constant for the reaction Fe2O3(g) + 3CO(g) <-> 2Fe(s) + 3CO2(g) is 2.5. Find the concentration of CO2, if at equilibrium the container has 1.50 mols Fe2O3, 0.75 mols CO, and 3.56 mols Fe.

So I think you don't use the Fe because it is a solid. Therefore:
2.5 = x^3/(1.50)(0.75^3)
So 1.58 = x^3
and x = 1.17 mols
So the concentration of CO2 is 1.17 mols. Is this correct?

Thank you!

For #1. Is that 3 mL? If so then all of the concns are incorrect since moles/LITER is concn. If it should be L, you appear to have done it correctly except that the denominator should be cubed and not squared.

For #2. Looks ok.
For #3. There is no volume listed.

Let's go through each question one by one and check your work:

1. Consider the following equilibrium reaction: 2PH3(g) <-> 2P(g) + 3H2(g)
To calculate Keq, you need to determine the concentrations of each species at equilibrium. Given that there is 0.70 moles of PH3, 0.49 moles of P, and 1.2 moles of H2 in a 3.0 mL flask, you need to convert these amounts into concentrations.

First, calculate the volume of the flask in liters: 3.0 mL = 3.0 x 10^(-3) L

Next, divide the number of moles by the volume to get the concentration in moles per liter:
[PH3] = 0.70 / 3.0 x 10^(-3) = 233.33 M
[P] = 0.49 / 3.0 x 10^(-3) = 163.33 M
[H2] = 1.2 / 3.0 x 10^(-3) = 400 M

Now, plug these concentrations into the equilibrium expression:
Keq = ([P]^2[H2]^3) / [PH3]^2
Keq = (163.33^2) * (400^3) / (233.33^2)
Keq = 2.66

So the correct value of Keq is 2.66, not 0.031.

2. When 250 g of chlorine is introduced into an evacuated 1.00 L flask and 25% of it dissociates into chlorine atoms, the reaction can be written as: Cl2(g) <-> 2Cl(g).

To calculate Keq, you need to determine the concentrations of Cl2 and Cl at equilibrium. Start by converting the mass of Cl2 to moles:
Cl2 moles = 250 g / molar mass of Cl2 = 250 g / 70.9 g/mol = 3.52 mol

Given that 25% of Cl2 dissociates, the concentration of Cl2 at equilibrium is:
[Cl2] = 3.52 mol * (1 - 0.25) / 1 L = 2.64 M

Since two moles of Cl are formed for every mole of Cl2 that dissociates, the concentration of Cl at equilibrium is:
[Cl] = 2 * 0.25 * 3.52 mol / 1 L = 1.76 M

Now, plug these concentrations into the equilibrium expression:
Keq = [Cl]^2 / [Cl2]
Keq = (1.76^2) / 2.64
Keq = 1.17

So the correct value of Keq is 1.17, not 2.46.

Since Keq in this case is less than 1, it indicates that the reaction favors reactants.

3. The equilibrium constant for the reaction Fe2O3(g) + 3CO(g) <-> 2Fe(s) + 3CO2(g) is given as Keq = 2.5.

To find the concentration of CO2 at equilibrium, given the amounts of Fe2O3, CO, and Fe, you need to consider the stoichiometry of the reaction.

Given that there are 1.50 moles of Fe2O3, 0.75 moles of CO, and 3.56 moles of Fe, you can see that the ratio between the moles of CO2 and CO is 1:3 according to the balanced equation.

Therefore, the moles of CO2 at equilibrium can be calculated as:
moles CO2 = 3.56 moles Fe * (1 mole CO2 / 2 moles Fe) = 1.78 moles CO2

So the concentration of CO2 is:
[CO2] = 1.78 moles CO2 / volume of the container (given in the question) = concentration

Without knowing the volume of the container, we cannot determine the concentration of CO2. Please check if the volume is provided in the question and use it to calculate the final result.

I hope this helps clarify the correct answers for you! Let me know if you have any further questions.