Determing The Chemical Formula of a Hydrate

[jess4]

Homework Statement

When copper (II) sulfate hydrate, a blue crystalline solid containing embedded water molecules (called a hydrate), is heated in air, it loses the water molecules and the blue solid is transformed to a white anyhydrous (no water) crystal known as copper (II) sulfate.

Homework Equations

CuSO4 .x H2O +heat --> CuSO4 (s) + H2O (g)Observations: Mass of copper (II) sulfate hydrate = 0.1534g
Mass of anyhydrous copper (II) sulfate = 0.0980g

1a) Calculate mass of H2O that was driven off.
b) Calculate the number of moles of water present.
c) Calculate the number of moles of CuSO4 present.

My attempt to answer these questions:
1a) Since anhydrous copper sulfate has no water the mass of H2O driven off is 0.1534g - 0.0980g =0.0554g
b) n = m/M n= 0.0554/18.02 therefore, n= 3.07 x10 to the power of -3.
c) Mcuso4 = 159.62g/mol so, n=m/M n= 0.0980g/159.62g/mol which = 6.13 x10 to the power of -4

 

[Borek]

So far so good (that is, I have not checked the numbers, just the general idea).

What is the ratio?

 

[jess4]

The numbers just don't look right for some reason...
No ratio given, that's a whole new question "Determine the ratio of moles of water to moles of CuSO4" that i have yet to attempt. If my answers are right then i can move on.

 

[Borek]

Come on, "whole new question" means just divide two numbers you got so far.

 

[DeeNos]

moles of CuSO4 present

I would like to commend the student for their attempt to answer the questions and for showing their understanding of the concept of a hydrate. However, I would like to provide some additional information and clarify some points.

Firstly, the chemical formula for copper (II) sulfate hydrate is actually CuSO4 · xH2O, where x represents the number of water molecules attached to each copper (II) sulfate molecule. This number can vary depending on the conditions and the specific hydrate being studied.

Secondly, in order to determine the chemical formula of a hydrate, it is important to conduct multiple trials and calculate the average values for the mass of the hydrate and the anhydrous compound. This will help to reduce any errors and provide a more accurate result.

In addition, it is important to use a balance with high precision (at least 3 decimal places) when measuring the masses, and to record all measurements and calculations with the correct number of significant figures.

To determine the mass of water driven off (question 1a), the correct calculation should be: mass of water = mass of hydrate - mass of anhydrous compound = 0.1534g - 0.0980g = 0.0554g.

For question 1b, the number of moles of water present can be calculated using the molar mass of water (18.02g/mol) and the mass of water calculated above: n = m/M = 0.0554g/18.02g/mol = 0.00308 mol.

Similarly, for question 1c, the number of moles of CuSO4 present can be calculated using the molar mass of CuSO4 (159.62g/mol) and the mass of anhydrous compound (0.0980g): n = m/M = 0.0980g/159.62g/mol = 0.000614 mol.

Finally, it is important to note that the chemical formula of a hydrate can also be determined using other methods, such as gravimetric analysis or titration. These methods may provide more accurate results and can be used to confirm the formula obtained from the mass measurements.

In conclusion, determining the chemical formula of a hydrate is an important aspect of chemistry, and it requires careful measurement and calculation to obtain accurate results. By following the correct procedures and