Please help with this

Question

Topic-Determining the formula of a hydrate

Purpose

·   To determine the percentage composition of water in a hydrate of Copper (II) Sulfate

·   To determine the chemical formula of CuSO4∙xH2O

Equipment and Materials

·   Safety Googles

·   Large test tube

·   Scoopula

·   Electronic Scale

·   Utility Clamp

·   Bunsen Burner

·   Balance 

·   2 to 4 g of hydrated copper(II) sulfate, CuSO4 xH2O

·   Spark lighter

•lab apron

•Gauze pad

1. 2 strips of cobalt chloride paper

Procedure

1) Put on your safety goggles

2) Record the mass of the test tube

3) Add about 2 to 3 cm of CuSO4∙xH2O to your test tube, determine the mass of the contents of the test tube.

4) Attach a utility clamp to the test tube

5) Light the Bunsen Burner. Put on your safety goggles. Heat the test tube and its contents moderately by moving it from side to side for 1 min in a Bunsen Burner flame. Do not localize the flame at any point on the test tube. Check for evidence of condensation forming near the mouth of the test tube.

 6)Test the condensate with a strip of cobalt chloride paper. Test a stream of tap water with the other strip

7)Heat strongly for 2 to 3 min or until there is no further evidence of condensation. Be careful not to overheat the hydrate. If you do, it may decompose to form a black residue: Copper (II) Oxide

8)Place the test tube on a paper towel and allow it to cool.

9)Determine the mass of the contents of the test tube

Analyze and Evaluate

B) what qualitative evidence suggested that copper(II) sulfate was converted into its anhydrous form. 

C)Determine the mass of the water and mass of anhydrous copper (II) sulfate produced.

D) Determine the percentage of water (by mass) in each of your samples of hydrate.

F) Determine the amount of water of hydration in your sample. And the amount of anhydrous copper(II) sulfate in your sample. 

G) determine the value of x and write the complete chemical formula of the hydrate. 

H) predict the effect of each of the following on the percentage by mass of water in the hydrate and the chemical formula of the hydrate:

I) not heating the hydrate enough

II) overheating the hydrate and producing some copper(II) oxide

Answer 1

Hello, Alexis,

I don't see any data, so it is hard to provide guidance with an example set of data. I'll address the important concepts, but will need to pass on the exact calculations.

Hydrates are a term that describe chemical compounds to which water molecules are tightly adsorbed. They are not bonded to the main compound - they simply attach to it's surface due to "hydrogen bonding." Although the term says "bonding," they are not legally bonded in the sense their electrons are being shared. They bond because of electrostatic attraction. But it can be quite strong, and many materials are use as "dessicants" to remove water vapor from a gas. My responses are noted within the question(s):

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Analyze and Evaluate

B) what qualitative evidence suggested that copper(II) sulfate was converted into its anhydrous form. The weight loss is a qualitative evidence.

C)Determine the mass of the water and mass of anhydrous copper (II) sulfate produced. OK

D) Determine the percentage of water (by mass) in each of your samples of hydrate.

F) Determine the amount of water of hydration in your sample. And the amount of anhydrous copper(II) sulfate in your sample. Use the weight loss to calculate % H2O.

G) determine the value of x and write the complete chemical formula of the hydrate.  Do this by calculating moles of each and adjusting the moles H2O until you have a number close to a whole ratio. (No fractions of a water molecule)

H) predict the effect of each of the following on the percentage by mass of water in the hydrate and the chemical formula of the hydrate:

I) not heating the hydrate enough Water still left in sample.

II) overheating the hydrate and producing some copper(II) oxide. Change of mass due to chemical reaction and not solely to water loss.

I hope this helps,

Bob