The reaction quotient will be equal to 0.718.
Here's how you can easily make a mistake when solving this problem. If you write the equilibrium like this
you can be tempted to write the reaction quotient,
You'd then go on to solve this equation and end up with
This is an excellent example of why you need to add the states of the species that take part in the reaction. Your equilibrium reaction actually looks like this
Since carbon is in a solid state, its concentration is not a part of the expression for neither
So, moving on with the explanation. The reaction quotient will tell you what the ratio between products and reactants is at a given moment during the reaction.
In your case, you know that at some point in the reaction, the reaction vessel contains that many moles of each species that takes part in the reaction.
Determine their concentration by using the volume of the reaction vessel
Therefore, the reaction quotient will be
You'd then go on to compare this value with the value given to you for the equilibrium constant,