1 (a)Hydroxylammonium chloride reacts with iron(III) chloride, FeCl 3 , in solut

Question

1 (a)Hydroxylammonium chloride reacts with iron(III) chloride, FeCl3, in solution to produce iron(II) chloride, HCl, H2O, and a compound of nitrogen. It was found that 2.00g of iron(III) chloride reacted in this way with 31.0 mL of 0.200M hydroxylammonium chloride. Suggest a possible formula for the compound of nitrogen so produced. This should be a known nitrogen compound.

(b)Arsenic(III) oxide, As2O3, can be titrated with potassium bromate in aqueous solution to produce potassium bromide and arsenic acid, H3AsO4. A mixture contained arsenic(III) oxide and arsenic(V) oxide, As2O5, and it was found that 1.000g of this mixture could be titrated in this way with 21.00 mL of 0.1000M KBrO3. What is the percentage by weight of each oxide of arsenic in the mixture?

Explanation / Answer

1/

mole FeCl3
2g(1mole/162.2g) = 0.012 mole
mole NH3OHCl
31.0ml(1L/1000mL)(0.2 mole/L) = 0.0062 mole
FeCL3 = 0.012/0.0062 = 1.9 = 2
NH3OHCl = 0.0062/0.0062 = 1
trial and error....
2 NH3OHCl + 4 FeCl3 ---> 4FeCl2 + 6HCl + H2O + N2O
N2O is nitrous oxide. accdg to http://en.wikipedia.org/wiki/Nitrous_oxi...
Nitrous oxide, also known as dinitrogen oxide or dinitrogen monoxide, is a chemical compound with chemical formula N2O. Under room conditions, it is a colourless non-flammable gas, with a pleasant, slightly-sweet odor. It is used in surgery and dentistry for its anaesthetic and analgesic effects, where it is commonly known as laughing gas due to the euphoric effects of inhaling it. It is also used as an oxidizer in internal combustion engines. In this use it is known as nitrous, or NOS after a well-known brand which has become a genericized trademark. Nitrous oxide is present in the atmosphere where it acts as a powerful greenhouse gas.

2.

First, write the equation for the reaction out, for both As2O3, as well as As2O5.

3As2O3 + 2KBrO + 9H2O -> 6H3AsO4 + 2KBr

Then, look at the equation to deduce the number of moles of arsenic (III) oxide that needs to react with 1 mole of KBrO3.

The number of moles of KBrO3 that was used to titrate the mixture, can be calculated by dividing 1.000M by 1000 (M = moles per litre), and then multiplying by 21(ml). You will get 0.021 moles.

Since according to the equation, the number of moles of As2O3 used was 1.5 (3/2) times of that of KBrO used, you can calculate the number of moles of As2O3 that reacted [0.021 x (3/2)] = 0.0315moles

Then, multiply it by its molecular mass [2(33) + 3(15.99)] = 113.97, and you will get the mass of As2O3.

After you've got the mass of As2O3, subtract that from the total mass of the mixture (1.000g) and you will obtain the mass of As2O5.

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