HELP! CHEMISTRY PROBLEMS...

Question

I can't figure out how to do these problems! Please help me if you know how to do them... If possible, explain how to do it so I can teach myself! THANK YOU IN ADVANCE! :)

1) The following reaction was performed:

Fe2O3 2X -> 2Fe X2O3

It was found that 79.847 g of Fe2O3 reacted with "X" to form 50.982 g of X2O3. Identify element X.

2) The molecular weight of an insecticide, dibromoethane, is 187.9 g/mol. Its molecular formula is C2H4Br2. What percent b mass of bromine does dibromoethane contain?

3) The Claus reactions, shown below, are used to generate elemental sulfur from hydrogen sulfide.

2H2S 3O2 -> 2SO2 2H2O

SO2 2H2S -> 3S 2H2O

How much sulfur (in grams) is produced from 48.0 grams of O2?

4) A 6.32 g sample of potassium chlorate was decomposed according to the following eqn:

2KClO3 -> 2KCl 3O2

How many moles of oxygen are formed?

5) Consider the following reaction:

CH4 4Cl2 -> CCl4 4HCl

What mass of CCl4 is formed by the reaction of 8.00 g of methane, (CH4) with an excess of chlorine?

Answer 1

I'm at work, so I'll answer more as I get time.

1.)

55.847 g Fe* 1 mol Fe/ 55.847 g Fe * 1 mol X2O3/2mol Fe * 2 mol X/1 mol X2O3

= 1 mol X

55.847 g Fe* 1 mol Fe/ 55.847 g Fe * 1 mol X2O3/2mol Fe * 3 mol O/ 1 mol X2O3* 16 g O/ 1 mol O

= 24 g O

50.982 g X2O3 - 24 g O = 26.982 g X

26.982 g X / 1 mol X = 26.982 g/mol…this is X’s molecular weight. Referring to out periodic table, we find that

X = Al

Thus,

Fe2O3(s) + 2Al(s) -->2 Fe(s) + Al2O3(s)

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2.)

Br2 = (2)(79.094 g/mol) = 158.19 g/mol / 187.9 g/mol

= 84.19 %

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3.)

Adding the reactions, we get:

4H2S + 3O2 --> SO2 + 3S + 4H2O

(48 g O2)( 1 mol O2/32 g O2) (3 mol S/3 mol O2) (32.065 g S/1 mol S)

= 48.09 g S

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4.)

6.32g KClO3 * (mol KClO3 /122.05 g) *(3 mol O2/2 mol KClO3)

= 0.0774 mol O2

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5.)

8 g CH4 *(1 mol/16.04 g CH4) *(1 mol CCl4/1 mol CH4)* (153.82 g/mol CCl4)

= 76.72 g CCl4

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Hope this helps