K and Q

[Andy_Yousif_1A]

Why is Q not equal to K if they have the same formula?

[Christian Hardoy 3F]

Q can be greater than, equal to, or less than K. Q is the reaction quotient and can be calculated at any point during a reaction. It has the same formula as K because it is used to determine if an equation is at equilibrium at a certain point during a reaction. Remember that the "formula" for K and Q gives you a ratio of products to reactants. K is the ratio when the reaction is at equilibrium. If Q is larger than K, it means that the numerator in the equation is larger than the numerator when the reaction is at equilibrium, meaning that the current amount of products is too large, relative to the amount of reactants. When Q > K, the reaction will proceed to the left, as the reaction moves back towards the equilibrium ratio. When Q < K, the numerator is smaller than the numerator when the reaction is at equilibrium, meaning that the current amount of products is too small, relative to the amount of reactants. In this case, the reaction will proceed to the right, as the reaction moves back towards the equilibrium ratio. When the system is at equilibrium, Q will equal K.

[Victor Qiu 1C]

K=Q only when the reaction is at equilibrium. K is the constant at equilibrium, while Q can be the constant at any time.
I think this website can help:
https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Equilibria/Chemical_Equilibria/Difference_Between_K_And_Q

[Kelly Yun 2I]

To give you a short and succinct explanation, Q is the reaction quotient where it's [products]/[reactants] at any point in the reaction. However, K is the same equation but at equilibrium, so there is just one K value for a given chemical reaction and its conditions.

[Michelle Nguyen 3F]

K is the equilibrium constant of a reaction while Q is the reaction quotient that can be found at any point of the reaction and will help you determine if the reaction is getting closer to equilibrium.

[Kathy_Li_1H]

Hi! K and Q are only equal to each other when the reaction is at equilibrium.

[Kelly Ha 1K]

Q is [products]/[reactants] at any point during the reaction and K is [products]/[reactants] at equilibrium. Q = K at equilibrium.

[Malakai Espinosa 3E]

Q is a more broad variable, as it can represent the ratio of P and R at any given time in the reaction, whereas K is only at equilibrium.

[Lung Sheng Liang 3J]

Q is the reaction quotient while K is the equilibrium constant. They both have the same formula but vary in values due to time.

[Bhuvan Kommineni 3L]

Q is for when the reaction is not at Equilibrium!

[Bai Rong Lin 2K]

Q would equal to K at equilibrium.

[Hannah Lechtzin 1K]

Q is the proportion of products and reactants when a reaction is not at equilibrium. This means that it is calculated the same way as K, but will not have the specific equilibrium concentrations. K is the concentration of products and reactions when a reaction is at equilibrium. I hope this helps!

[Mina Tadros 3L]

Q is the reaction quotient, which is the ratio of products to reactants that are not at equilibrium. In contrast, K is the equilibrium constant, which is also the ratio of products to reactants, but they have already reached equilibrium.

[Jack Kettering 3D]

Q is at any point not at equilibrium and K is only when the reaction is at equilibrium so they will have different values

[Jeremy Wei 2C]

They have different values since Q is the ratio between products and reactants at any point in the reaction, while K is while at equilibrium.

[Morgan Gee 3B]

Q follows the same formula for K but at any given set of concentrations. On the other hand, K is the constant for equilibrium.

[Sejal Parsi 3K]

Q is equal to K at equilibrium, and Q is when the reaction is not at equilibrium.

[Jaclyn Schwartz 1I]

So K is the equilibrium constant. Q is the reaction quotient because it can occur at any point of time during the equation. If Q=K, that meaNs the equation is at equilibrium.

[Joanna Huang]

K is the concentrations of the products over reactants AT EQUILIBRIUM, but Q is the concentrations of the products over reactants NOT AT EQUILIBRIUM.

[Charmaine Ng 2D]

Q has the same setup as K, but measures when the solution is not at equilibrium. Therefore, Q=K at equilibrium.

[Jose Miguel Conste 3H]

K is when it is at equilibrium while Q is at a specific time during the reaction

[Teti Omilana 1G]

Q and K are both products over reactants, but K is used at equilibrium while Q is used at any other point during the reaction. If Q=K, that means the reaction is at equilibrium.

[Darlene Lien 3E]

Q represents the ratio of products and reactants at any time during the reaction (not at equilibrium) while K represents the ratio at equilibrium. At equilibrium, Q=K.

[YuditGaribay3J]

Would the values of Q (products and reactants) be given when we are solving the problem? This is what has always confused me.

[Brianna Chen 3F]

While Q can be calculated at any point in the reaction, K can only be calculated when the reaction is at equilibrium.

[Diana Aguilar 3H]

Like many others have stated, Q is equal to K at equilibrium, while Q is mainly used when the solution is not at equilibirum.

[IshanModiDis2L]

To restate, the value of Q can be calculated at any point in any given reaction. However, K can only be calculated when the reaction is at equilibrium.

[AlbertGu_2C]

K is Q at equilibrium, whereas Q can be either at equilibrium or not

[Muskaan Abdul-Sattar]

So, both are constants but K will only be equal to Q when the reaction is at equilibrium. This is because Q can be the constant at any point, but K has to be the constant at equilibrium.

[Jacob Schwarz-Discussion 3I]

Because Q isn't always at equilibrium. K always equals Q when Q is at equilibrium.

[FrancescaHawkins2H]

Q is not equal to K because K is specifically the ratio of products to reactants when the reaction is at equilibrium, hence the name equilibrium constant. Q is also the ratio of products to reactants but it implies that the chemical reaction is not at equilibrium.

[Audrey Banzali-Marks 1A]

Q differs from K because you calculate the two at different points of the reaction. For example, if you calculate Q at the beginning of a reaction, it would be very small since there is more reactant than the product. However, if you calculate Q at equilibrium, it would give you the value of K because K is the ratio of reactants and products when the reaction is at equilibrium. You can only calculate K at equilibrium, whereas you can calculate a reaction quotient Q at any point in the reaction.

[Talia Tam 3L]

K=Q when the reaction is at equilibrium. K is the equilibrium constant, while Q is the reaction quotient. Q is the ratio of products and reactants at any time during the reaction.

[elliemehrara]

K is the equilibrium constant, while Q is the reaction quotient. Although K and Q can be equal if the system is at equilibrium, this is not always the case. Q is calculated by plugging the concentrations or pressures of each species in the system at any point (not necessarily when the system is at equilibrium) into the formula.

[Tammy Shen 2L]

You can think of K and Q as similar, but we only use K when we know that the reaction is at equilibrium. If we are only representing the ratio between reactants and products and the reaction isn't at equilibrium, we represent it as Q.

[Santiago Cortes 2J]

Q and K do have the same formula. However K is the constant once the reaction is at equilibrium while Q is the reaction quotient at any point in the reaction. Therefore, Q can be either larger, smaller, or equal to K.

[Mario Prado 1K]

Hello,

Q is actually equal to K in one case and that's when it is the ratio of the reaction at equilibrium. It's at this number when Q becomes K since this basically the definition of K, but any other ratio of products to reactants that doesn't equal K is solely Q.


Hope this helps.

[Michelle Argueta 1E]

They are not the same as they occur at different times. Despite having the same ratio of [products]/[reactants], Q refers to the reaction quotient at any point in the reaction, while K refers to the equilibrium constant that only occurs when the reaction has reached equilibrium.

[Holly Do 2J]

They are not equal to each other because Q is when the reaction is NOT at equilibrium meaning we input different concentrations/partial pressures while K is when the reaction IS at equilibrium and thus K is a constant number for that specific reaction.

[Eric Sun 2G]

Q is the calculation of the ratio between products and reactants at a given time, meaning that the reaction could potentially not be at equilibrium at that moment. Thus, Q could be different from K.

[Lesley Kim 1K]

Q and K have the same formula, but they are used under different conditions. K is essentially the same thing as Q, but can only be labeled K because the system is at equilibrium. Think of K as a "fancy" version of Q that is special because its ratio is the equilibrium constant ratio rather than any other value.

[Ruirui Lan]

Hi, although they have the same formula, they are used in different contexts. K is a constant which is used when a chemical reaction is at equilibrium at a certain temperature. Q, however, is a quotient of activities of both the reactants and the products at any instant, any stage of the chemical reaction process. Therefore, it's crucial to design such a difference if people want to measure and compare the concentration of reactants and products of a certain arbitrary stage to the concentration values when the chemical reaction is at equilibrium.

[Michelle Gong]

K is when the system is at equilibrium, Q is when they are not, so while you calculate them with the same formula, they are being calculated at different stages of the rxn, if that makes sense!

[Terrence Chi]

Hi, Q is a quantity that changes as a reaction approaches equilibrium however, K is the numerical value of Q at the end of the reaction, when equilibrium is reached. Hope this helps!

[Jessica Li 1G]

K is only equal to Q when a reaction is at equilibrium. However, Q is different from K since Q can represent the constant at any point in the reaction, whereas K is only the constant at equilibrium.

[cnyland]

Q and K are simply different variables to represent the same equation, but at DIFFERENT points. K is the products over reactants while the system is at equilibrium and Q is the products over reactants while the system is not at equilibrium. So, if you want to check if a system is at equilibrium, and you have a known k value for an equation, you can calculate Q and see if it is less than or greater than k, and in the case that the value of Q is equal to the known K value, then you know that the system is at equilibrium because at equilibrium Q=K!

[Veronica Larson- 1I]

Q and K are calculated in the same way, but because K is referring to the ratio of products to reactants at equilibrium and Q can be at any point in the reaction, the concentrations used might be different and therefore give you a different value. At equilibrium, K=Q, but at other points in the reaction Q can be greater than or less than K.

[Jessica Servoss 1H]

K is the value we get only at equilibrium. Q could be any value greater than or less than K, and tells us that the reaction is not yet at equilibrium if Q doesn't equal K. So, Q can equal K, but only when the reaction has reached equilibrium.

[Amanda Pineda 3H]

K represents the equilibrium constant when the reaction is actually at equilibrium. Q represents the reaction quotient which represents any time during the reaction.

[Kathryn Heinemeier 3H]

K is designated for when the reaction is at equilibrium while Q can be at any time during the reaction

[Muryam_Hasan_2I]

Q can be equal to K, but not always. This is because K is restricted to defining systems at equilibrium, whereas Q can be taken at any point in the reaction. This is how Q is used to determine whether or not a reaction is at equilibrium: because they have the same formula, if they are not equal, the system is not at equilibrium.

[gracebinder3I]

Hi!
While Q and K have the same formula, Q finds a value for reaction concentrations NOT at equilibrium, whereas K is always defined for equilibrium concentrations. Therefore, Q and K can be compared such that at certain points in the reaction, Q = K (as you said), but Q > K or Q < K. This comparison determines whether the reaction favors reactants, products, or neither.
I hope this helps!

[Chris Van 2J]

Although Q and K have the same formulas, we would use Q when the reaction is not at equilibrium. K is defined as the equilibrium constant when the reaction is at equilibrium.

[Trisha Badjatia 2L]

K is the equilibrium constant, while Q is a reaction constant that can be taken at any point in time of the reaction. Thus, you can compare Q to K to see which side the reaction will move toward to reach equilibrium. If Q > K, then the reaction will move to the left to increase the concentration of the reactants. If Q < K, then the reaction will move to the right to increase the concentration of the products.

[205705413]

K is the equilibrium constant, calculated when the reaction is at equilibrium. Q can be calculated any time, and can be a good way to see whether the reaction is favored in the forward or backward direction.

[Clarence Clavite 2K]

They are not equal because Q is the constant at a certain time during the reaction, not at equilibrium. The comparison of Q and K tells us whether the reactants or products are favored.

[Vanessa Wiratmo 3k]

Although they are calculated in the same fashion (which is the concentration/partial pressure of products divided by the concentration/partial pressure of the reactants) they are different in what they represent. The K value is an equilibrium constant. When a reaction reaches equilibrium, there is no net changes as the formation of reactants and products are happening at the same rate. K should be the same regardless if someone performed the experiment with one grams vs 1000 grams at a given temperature. The Q value however, is a ratio that is taken at whatever point of the equilibrium reaction to tell whether the experiment has reached equilibrium yet. If Q=K, that means the reaction has reached equilibrium. If Q<K, that means not enough time has passed and the forward reaction is still happening. The reaction is still going towards the products. If Q>K, then that means there are too many products. At this point, it is important to check whether the correct temperature is being used.

[Jessica Sun 2I]

K is the equilibrium constant while Q is the reaction quotient. The difference is that K only equals Q when the reaction is in equilibrium.