The chemical formula of a salt A, is written FexCly. ZH2O. A sample of this salt of 0.5 grams was dissolved in water. The resulting solution was poured into a chemical beaker containing silver nitrate. The precipitate formed, AgCl, was collected, dried and weighed, AgNO3 Calculate a) the number of moles of precipitate. AgCl, when it is known that its mass is 0.718 grams; b) the number of moles of chloride contained in 0.5 grams of compound A; c) the mass in grams of chloride ions present in 0.5 grams of compound A. ii. By dissolving in water a sample of 0.5 grams of the above compound A 25 ml of solution was obtained, which was then titrated with 25 ml of 0.02 M KMnO4 solution. The reaction that occurs in this case is as follows: MnO4 + 5Fe2 + + 8H → → Mn2 + + 5 Fe3 + + 4H20 Count: a) the number of MnO4 'moles that have entered the reaction; b) the mass in grams of Fe2 + ions in the sample; c) the number of moles of Fe2 + ions in it: d) the mass of water in 0.5 grams of compound A; e) the number of moles of water contained in 0.5 grams of compound A: f) the values of x, y and z in the chemical formula of compound A.

first, consult an activity series chart to determine if al is more reactive than fe. it is, so it will replace the fe. now, one can continue with the problem.

next, make sure you have a correctly balanced equation.

3feo + 2al ==> 3fe + al2o3

now, determine which reactant (feo or al) is in limiting supply.

moles feo present = 125 g x 1 mole/71.8 g = 1.74 moles

moles al present = 25.0 g x 1 mole/26.98 g = 0.927 moles

since from the balanced equation, it take 3 mol feo for every 2 mol al, al will be limiting.

you can determine this simply by dividing moles of each by their coefficient in the balanced equation. for example: 1.74/3 = 0.58 and 0.927/2 = 0.464. al is less, so it is limiting.

finally, using the stoichiometry in the balanced eq. determine mass of fe that can be produced from 0.927 moles of al.

0.927 moles al x 3 moles fe/2 moles al x 55.8 g/mole = 77.6 g

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definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.