• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Determining the water of crystalisation

Extracts from this document...


DETERMINING THE WATER OF CRYSTALLISATION Aim: The lab is to determine the number of moles of water of crystallization in crystals of a hydrated salt CuSO4*xH2O by heating it to constant mass in a crucible. Apparatus: * weighing machine * crucible * hydrated copper (II) sulfate * tripod * pipe clay * burner * stick Method: 1. Weigh an empty crucible and record the result as accurately as possible 2. Fill the crucible approximately to one-third with crystals of the salt that you have been given (in this case copper (II) sulfate pentahydrate) and hence reweigh it 3. Heat the crucible strongly on a pipeclay triangle constantly stirring till it changes the blue colour to white-blue and then leave it to cool. 4. When it is cool enough to hold it in your hand, reweigh it 5. Heat again for a few minutes constantly stirring, then leave it to cool and reweigh 6. ...read more.


salt: before heating 31.56 g after first heating 30.85 g after second heating 30.84 g Table 4: Masses of hydrated salt and anhydrous salt; mass of water Mass of hydrated salt 1.98 g Mass of anhydrous salt 1.26 g 1.98 - 1.26 = 0.72 Mass of water in hydrated salt 0.72 g Using the molar mass of the anhydrous salt I used I was able to calculate the number of moles of anhydrous salt that remained after heating. MCuSO4= 63.55+32.07+15.99*4=159.58 g 1 mole of CuSO4 -------- 159.58 g X ---------- 1.26 g X=(1 mole*1.26g)/159.58 g X=0.007896 moles of CuSO4 Rounded to 6 decimal place Then, the mass and number of moles of water that was lost from the salt were calculated. 31.56 g - 30.84 g = 0.72 g MH20=15.99+2*1.01=18.01 g 1 mole of H2O -------- 18.01 g X --------- 0.72 g X= (1 mole*0.72g)/ 18.01 g X=0.039978 moles of H2O Rounded to 6 decimal place After calculating both number of moles, I was able to calculate the number of moles of water that are combined with one mole of the salt. ...read more.


Additionally, the crystal should not be to small. Errors also occurred when re-weighting the crucible. It was important to cool the crucible before weighting. Not only was it for our safety, but also for the precision of our measurement as the weighting machine could be influenced by heat. So an error could occur. An error could come up while stirring. It is possible that part of our substance was left on the stick what cause further errors. To improve the experiment * larger portion of salt * lid on the crucible (to avoid loss of crystals) * wider crucible (easier to heat) * more measurements * more time to cool down the crucible * weighting machine with more decimals (to lower the uncertainties) could be used. Also, there are some hydrates, which don't decompose before reaching their boiling point. For those, the method used in the experiment is not suitable. Removing water from melted form and crystalliation from anhydrous salt could be adopted. ?? ?? ?? ?? Gracja Kowalska kl.II ib 2008-10-31 ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our International Baccalaureate Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related International Baccalaureate Chemistry essays

  1. Chemistry Lab Report. AIM: To calculate the number of molecules of water of ...

    be assumed that there are 5 molecules of water of crystallization in hydrated copper sulphate. ERROR ANALYSIS: % Error in the electronic balance = +-(0.01)(100)/2.5 = +- 0.4% %Error in the electronic balance = +-(0.01)(100)/1.656 = +-0.6% Total systematic error= +-1%.

  2. Water of crystallization of BaCl2.xH2O

    Evaluation: Percentage error = In this case, all the uncertainties for recorded mass in the table below is because it's the result of the subtraction of values with uncertainties , which are mass of the crucible + lid + hydrate and mass of crucible + lid + anhydrous salt.

  1. Crystallization - Rock candy is collection of sugar crystal.

    Furthermore after applying smear grease (such as Vaseline) or oil (cooking or mineral oil) on the part of the thread above the solution to prevent the solution from creeping up the thread. Once have placed the rod in the beaker and have allowed the solution to form its crystal one in room temperature and the other in the fridge in a safe place.

  2. Dissolved Oxygen in water

    Step 5: Let the sample stand and the flocculent precipitate will start to settle. 10. Step 6: After approximately 2 minutes, when the upper half of the bottle becomes limpid, add 10 drops of Sulphuric acid solution. 11. Step 7: Again stopper the bottle and invert it until all particulate material is dissolved.

  1. Percentage of Water In Popcorn

    The gamma kernels are composed of 16.7%, 15.7%, and 14.8% water, while the delta kernels contain 19.4%, 17.0%, 19.0% water for trials 1, 2, and 3 respectively. (Refer to appendix for original data and calculations). See Table 1 - Percentage of Water in Popcorn Beta, Gamma, and Delta The data

  2. PURPOSE To determine the amount of water of crystallization in one mole of a ...

    With the crucible still on the balance, added approximately 2 grams of the hydrated salt to the crucible. Then I recorded the mass. 3. Heated the crucible gently on a burner for 3-5 minutes and covered it. Was careful not to allow the crucible to turn red, as overheating decomposes the sample.

  1. The chemistry of atmospheric and water pollution.

    Decreases plant growth Affects aquatic organisms CFCs also contribute to the problem of the enhanced greenhouse effect. (The enhanced greenhouse effect is caused by gases, released by human activity, absorbing heat rays that come from the Earth's surface, and then emitting the heat rays.

  2. Hydrated Crystals Lab. In the experiment of Hydrated Crystals the formula for the ...

    The number of moles of anhydrous salt of CuSO4 is 0.0110 �0.04 and the number of moles of water is 0.0722 �0.06. Calculations: MgSO4 + hydrate = 3.08 �0.03g MgSO4 after heated is = 1.76 �0.03g MgSO4 + hydrate - MgSO4 after heated = 3.08g - 1.76g = 1.32g �0.06 of water MgSO4 (anhydrous salt)

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work