# Finding a stoichiometric coefficient

• rustynail
In summary, the problem involves determining the value of gamma in a sample of CuSO_4 * gamma H2O with known percentages of Cu, S, O, and H. The solution involves finding the molar mass of the compound, taking into account the hydration part, and using approximations to get closer to an integer coefficient.
rustynail
Hello, I am currently taking a college level chemistry class. I am struggling with this problem, any help would be greatly appreciated.

## Homework Statement

We have a certain quantity of

$$CuSO_{4} \cdot \gamma H_{2}O$$

If our sample is formed of (25,5% Cu), (12% S), (57,7% O) and (4.04% H), what is the value of gamma ?

None given.

## The Attempt at a Solution

I have determined the mass of 1mol of each element, the mass of 1mol of CuSO_4 (111.611g) and really, I'm stuck there.

Please don't spoil the fun for me, just give me some hints.

(edit) : I have done this much more :

Mass of 1mol Cu = 63.546g

(63.546g/111.611g)*100 = 56.94% Cu in CuSO_4

56.94%/25.5% = 2.2328 (increment factor)

So the mass of the hydrated CuSO_4 should be

111.611g * 2,2328= 249.21g

249.21g - 111.611g = 137.6g H2O

and 137.6g/18(g/mol)= 7.6 mol H2O

but it does not give me an integer...

Last edited:
Try some Approximations in calculations. For example, Molar Mass of Cu is good as 63.5.

thanks AGNuke, you mean that some approximations could get me closer to an integer coefficient? Do you think my attempt at a solution made sense?

Last edited:
No. You can apply the percentage "after" you had taken the molar mass of all the compound (including the hydration) part in consideration.
Take molar mass of compound as M[CuSO4]+γ[M(H2O)]

Also, you took the molar mass of CuSO4 incorrect.

And don't panic if you don't get answer in integer. Just try rounding them up or down.

Hello! It looks like you have made some good progress so far. To find the stoichiometric coefficient (gamma), you will need to use the molar ratio between Cu and H2O in the compound CuSO4·γH2O. This means that for every 1 mole of Cu, there should be γ moles of H2O.

You have already calculated the mass of 1 mole of Cu and the mass of 1 mole of CuSO4. To find the mass of 1 mole of H2O, you can subtract the mass of 1 mole of CuSO4 from the total mass of the compound. Then, use the molar mass of H2O to convert this mass to moles.

Once you have the moles of H2O, you can use the molar ratio between Cu and H2O to solve for gamma. Remember, the molar ratio is the ratio of moles of one element to moles of another in a compound.

I hope this helps! Keep up the good work and don't hesitate to ask for more clarification if needed. Good luck!

## 1. What is a stoichiometric coefficient?

A stoichiometric coefficient is the number that represents the relative amount of a substance in a chemical reaction. It shows the ratio in which reactants and products combine and is used to balance chemical equations.

## 2. How do you find the stoichiometric coefficient?

The stoichiometric coefficient can be found by balancing the chemical equation. This involves adjusting the number of molecules or moles of each substance to ensure that the number of atoms on the reactant side is equal to the number of atoms on the product side.

## 3. What is the importance of finding the stoichiometric coefficient?

Finding the stoichiometric coefficient is important because it allows us to accurately predict the amount of reactants needed and the amount of products that will be produced in a chemical reaction. It also helps to understand the relationship between different substances in a reaction.

## 4. Can the stoichiometric coefficient change?

Yes, the stoichiometric coefficient can change depending on the conditions of the reaction. For example, if the temperature or pressure is altered, the coefficients may also change to maintain the balance of the equation.

## 5. What are some common methods for finding the stoichiometric coefficient?

Some common methods for finding the stoichiometric coefficient include using the mole ratio method, the oxidation number method, and the inspection method. These methods involve manipulating the coefficients in a chemical equation to achieve a balanced equation.

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