# Solve Concentration Problem: K, Cr2O7, Equilibrium

• Euler2718
In summary: The equilibrium constant is [products]/[reactants], so the coefficients are just telling you how much of each product is present at equilibrium.

Question 9)

## Homework Equations

$$K=\frac{[P]}{[R]}$$

## The Attempt at a Solution

What is confusing me is the wording. It merely says for the concentration of chromate. All this time we've been doing the equilibrium concentrations. Doing mole-mole with the Cr2O7 yields the answer to be D. I then assumed that it meant that they were the concentrations at equilibrium, which gave C to be the correct answer after preforming the equilibrium constant equation. Thanks for reading.

Not sure what you mean by "doing mole-mole". I read the question as if 0.100 M was the equilibrium concentration, not the initial.

Borek said:
Not sure what you mean by "doing mole-mole". I read the question as if 0.100 M was the equilibrium concentration, not the initial.

Forgive me. Mole to mole ratio is what I meant to convey. Thank you for your input.

In other words you tried to calculate equilibrium concentration following the stoichiometry?

Where did you got OH- from?

Morgan Chafe said:

## Homework Statement

Question 9)

View attachment 77944

## Homework Equations

$$K=\frac{[P]}{[R]}$$

## The Attempt at a Solution

What is confusing me is the wording. It merely says for the concentration of chromate. All this time we've been doing the equilibrium concentrations. Doing mole-mole with the Cr2O7 yields the answer to be D. I then assumed that it meant that they were the concentrations at equilibrium, which gave C to be the correct answer after preforming the equilibrium constant equation. Thanks for reading.

What is the expression for the equilibrium constant for this particular equilibrium?

True, it has [products] in the numerator and [reactants] in the denominator, but what do you do with the stoichiometric coefficients?

As Borek notes, they are giving you equilibrium values for the concentrations. If they weren't they would say something like "... the inital concentration of dichromate beofre equilibrium is reached is blah blah..."

Quantum Defect said:
As Borek notes, they are giving you equilibrium values for the concentrations. If they weren't they would say something like "... the inital concentration of dichromate beofre equilibrium is reached is blah blah..."

Yes. The issue was if they were equilibrium values or not. Usually it explicitly states.

Morgan Chafe said:
Yes. The issue was if they were equilibrium values or not. Usually it explicitly states.
What is the expression for the equilibrium constant, using concentrations? Where do the stoichiometric coefficients come in?

## 1. What is the definition of concentration in chemistry?

Concentration in chemistry refers to the amount of a substance (solute) dissolved in a given volume of solution (solvent). It is typically measured in units of moles per liter (M) or grams per liter (g/L).

## 2. How do you calculate the concentration of a solution?

The concentration of a solution can be calculated by dividing the number of moles of solute by the volume of the solution in liters. For example, if 0.5 moles of KCl are dissolved in 1 liter of water, the concentration would be 0.5 M (0.5 moles / 1 L = 0.5 M).

## 3. What is the equilibrium constant for a chemical reaction?

The equilibrium constant, denoted by K, is a measure of the extent to which a chemical reaction will proceed towards products at a given temperature and pressure. It is calculated by dividing the concentration of products by the concentration of reactants, with each concentration raised to the power of its respective coefficient in the balanced chemical equation.

## 4. How does the equilibrium constant relate to the concentration of reactants and products?

The equilibrium constant, K, is directly related to the concentrations of reactants and products in a chemical reaction. As the concentrations of reactants and products change, the value of K will also change. A larger value of K indicates that the reaction favors the formation of products, while a smaller value of K indicates that the reaction favors the formation of reactants.

## 5. How can you use the equilibrium constant to solve concentration problems?

In order to solve concentration problems involving equilibrium, you can use the equilibrium constant, K, along with the initial concentrations of reactants and products to calculate the concentrations at equilibrium. This can be done using the equilibrium expression and solving for the unknown concentration. Additionally, the value of K can be used to determine the direction in which the reaction will proceed to reach equilibrium.