Describe how you could find the % by mass of water in the hydrate CuSO4Ÿ5H2O assuming that you
did not already know the formula. Be specific and list the laboratory procedural steps you would take
in the order that you would perform them.
What this question is looking for is a very detailed answer, the procedure to follow if you will, and no one here will write up a procedure for you. However, I can give you the basic steps and you and can add to it.
Weigh the sample, heat to drive off the water, and weigh again. The difference in weight is the amount of water lost. Then convert to percent.
To find the % by mass of water in the hydrate CuSO4·5H2O without knowing the formula, you can use a laboratory procedure known as the "heating to constant mass" method. Here are the step-by-step procedures:
1. Weigh the empty crucible accurately using an analytical balance. Record the mass.
2. Add a small amount of the hydrate sample (CuSO4·5H2O) to the crucible. Note down the mass of the crucible and the sample combined.
3. Place the crucible with the sample on a tripod stand and heat it gently using a Bunsen burner. Initially, keep the flame low to avoid splattering or loss of the sample.
4. Gradually increase the heat, ensuring that the crucible is evenly heated. This process drives off the water from the hydrate, leaving the anhydrous salt behind.
5. Continue heating until you observe that no more water is being given off. You can test for the presence of water vapor by holding a piece of cold glass above the crucible. If condensation occurs, more heating is required.
6. Once you are confident that all the water has been driven off, remove the crucible from the heat and allow it to cool.
7. Weigh the crucible containing the anhydrous salt. Record the mass.
8. Repeat this heating and cooling process until the mass of the crucible and anhydrous salt remains constant. This indicates that all the water has been driven off, and you have obtained the compound without any water content.
9. Calculate the mass of water lost by subtracting the final mass of the crucible and anhydrous salt from the initial mass of the crucible and sample.
10. To calculate the % by mass of water in the hydrate, divide the mass of water lost by the initial mass of the sample (hydrated salt), and then multiply by 100.
Following these steps will allow you to determine the % by mass of water in the hydrate CuSO4·5H2O even without initially knowing the formula.