CHEMESTRY

a student heats 2.005 g of a copper bromide hydrate of unknown molecular formula, completely driving off the water of hydration, and notices that the weight drops to 0.998g. Upon reduction with excess aluminum metal, the copper ions are reduced to 0.442 g of Cu (s). determine the formula of this unknown copper bromide hydrate

  1. 👍 0
  2. 👎 0
  3. 👁 404
  1. 2.005 = mass CuxBry + H2O
    0.998 = mass CuxBry
    ----------
    1.007 = mass water

    CuxBry + Al ==> Cu + ...not balanced.
    0.998g.........0.442
    moles Cu = 0.442/atomic mass Cu = about 0.007 but you need to be more exact.
    So mols CuxBry must be 0.007

    n = grams/molar mass and
    molar mass = grams/n = 0.998/0.007 = about 143 or so for molar mass CuxBry.
    143 = mass Cu + mass Br
    -63.5 = mass Cu
    ------------
    79.8 = approximate mass Br which is one Br so the formula must be CuBr.
    Find moles CuBr (0.998/molar mass) = ?
    mole H2O = 1.007/18 = ??
    Now find the ratio H2O to 1 mole CuBr. The easy way to do this is to divide the smaller number by itself (which gives you 1.000) and divide the other number by the same small number. Round to whole number. That should give you x in CuBr.xH2O.

    1. 👍 0
    2. 👎 0

Respond to this Question

First Name

Your Response

Similar Questions

  1. Chemistry

    A hydrate of copper (II) sulfate with formula CuSO4.xH2O has a molar mass of 250.0 g/mol. 2.545 g of hydrate is heated and 63.85% of the residue is found after heating. a) Determine the value of x in the formula of the compound b)

    asked by Kai on June 17, 2017
  2. Chemistry

    SOMEBODY PLEASE HELP ME! This is my last question for the chemistry and thank you. :D A BS Medical Technology student was asked to determine the molecular weight of a diprotic acid using acid-base titration. This student performed

    asked by Shiro on May 6, 2020
  3. chemistry

    A 2.50g sample of a hydrate of calcium nitrate was heated, and only 1.70g of the anhydrous salt remained. what is the formula of the hydrate?

    asked by rose on February 21, 2013
  4. Chemistry

    A BS Medical Technology student was asked to determine the molecular weight of a diprotic acid using acid-base titration. This student performed four trials. Firstly, the student used potassium hydrogen phthalate (KHP, 204.22

    asked by el on May 14, 2020
  1. Chem 11

    So I did a lab determining the chemical formula of a hydrate. I really just need somebody to check this over for me. We had to find the molecular formula of a hydrate of copper (2) sulphate, CuSO4 .xH2O. My observation table looks

    asked by Katherine on November 18, 2014
  2. Chemistry

    A sealed flask contains 1 mole of hydrogen and 3 moles of helium gas at 20DC. If the total pressure is 40kPa, what is the partial pressure of the Hydrogen gas? AND :) The data below was obtained by a student in order to determine

    asked by Christina on March 31, 2013
  3. science

    (1) A sample of the hydrate CuSO4.5H2O has a mass of 12.5g. (a) how many molecules of hydrogen are contained in this hydrate? If the hydrate is completely dehydrated.

    asked by chancy xdicey on August 27, 2015
  4. Chemistry

    Cobalt(II) chloride is commonly obtained from chemical supply houses as a hydrate with the formula CoCl2 • 6 H2O. An analysis showed that 25.0 g of this hydrate contains 11.3 g of water. What is the percent water by weight in

    asked by Destiny on February 19, 2019
  1. science

    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

    asked by cara on April 1, 2009
  2. chemistry

    Criticize the following statements. 1. In an ionic compound, the number of cations is always equal to the number of anions. [Is it ok to say 'not always'?] 2. The molecular formula for strontium bromide is SrBr(sub 2) [what's

    asked by Chris on September 25, 2006
  3. Chemistry 11

    So I did a lab determining the chemical formula of a hydrate. We had to find the molecular formula of a hydrate of copper (2) sulphate, CuSO4 .xH2O. My observation table looks like this: Mass of clean, dry test tube: 21.6g Mass of

    asked by Katherine on November 18, 2014
  4. chemistry

    In a reaction involving the iodination of acetone, the following volumes were used to make up the reaction mixture: 10 mL 5.0 M acetone + 10 mL 1.5 M HCl + 10 mL 0.005 M I2 + 20 mL H2O A student found that it took 400 seconds for

    asked by leticia on March 5, 2015

You can view more similar questions or ask a new question.