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I did a hydrate lab in school and these were my results and at the end we have to write the correc formula for the hydrate but I know the answer at the end is supposed to be 5H2O so why do I keep getting 4H2O? Can someone double check my work

Mass of evaporating dish 35.88


Mass of Dish and hydrated chemical 39.46


Calculated mass of hydrated chemical only 3.58


Mass of dish and chemical after 1st heating 38.40


Mass of dish and chemical after 2nd heating 38.40


Mass of dish and chemical after 3rd heating (if needed)


Now calculate the following:

Mass of anhydrous chemical only 38.40-35.88= 2.52 g


Mass of water lost. 1.06 g


% of hydrate the anhydrous chemical is. 2.52/3.58= 70.39%


Molar Mass of anhydrous Copper (II) sulfate 159. 6


226.7


Molar weight of water lost 67.2

Total number of moles of water
226.7-159.6= 67.1 67.1/18.02= 3.723 mols= 4

Prefix
tetra

Correct formula for the hydrate
CuSo4 4H20

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4 answers
  1. Mass of evaporating dish: 35.88 g

    MAss of dish and hydrated chemical
    39.46 g


    Calculated mass of hydrated chemical only
    3.58 g


    Mass of dish and chemical after 1st heating

    38.40


    Mass of dish and chemical after 2nd heating
    38.40

    Mass of anhydrous chemical only
    38.40-35.88= 2.52 g

    Mass of water lost
    3.58-2.52= 1.06 g

    % of hydrate the anhydrous chemical is
    2.52/3.58= 70.39%

    Mollar mass of anhydrous copper (II) sulfate: 159.6 grams


    Molar mass of hydrated sopper (II) sulfate: 159.6/.7039 = 226.7 g

    Molar weight of water lost: 226.7-159.6= 67.2

    Total number of moles of water

    67.1/ 18.02 = 3.723 which is about 4 mols

    Prefix: tetra

    formula for hydrate: CuSO4 4H20

    WHERE DID I GO WRONG??? ITS really supposed to be 5H2O

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  2. Mass of water lost
    3.58-2.52= 1.06 g

    % of hydrate the anhydrous chemical is
    2.52/3.58= 70.39%

    Mollar mass of anhydrous copper (II) sulfate: 159.6 grams


    Molar mass of hydrated sopper (II) sulfate: 159.6/.7039 = 226.7 g

    Molar weight of water lost: 226.7-159.6= 67.2

    Total number of moles of water

    67.1/ 18.02 = 3.723 which is about 4 mols

    Prefix: tetra

    formula for hydrate: CuSO4 4H20

    WHERE DID I GO WRONG??? ITS really supposed to be 5H2O

    1. 👍
    2. 👎
    3. ℹ️
    4. 🚩
  3. Prefix: tetra

    formula for hydrate: CuSO4 4H20

    WHERE DID I GO WRONG??? ITS really supposed to be 5H2O

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    2. 👎
    3. ℹ️
    4. 🚩
  4. I had the same problem to. It could have been due to the loss of water of crystallization to the atmosphere before the sample was heated. In my case, I got a trihydrate.

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