Unit 1 - Formula and reaction quanitites

Question 1

What is the formula for Copper (II) Chloride

Answer 1

CuCl₂

Question 2

What is the fomulat for disulphur pentachloride

Answer 2

S₂Cl₅

Question 3

Formula for Magnesium Sulfate

Answer 3

(finished in -ate) look page 8

Potassium Sulfate

K SO₄

1+ 2-

2 1

K₂SO₄

Question 4

Formula for Ammonium phosphate

Answer 4

Ammonium phosphate

NH₄ PO₄

1+ 3-

3 1

(NH₄)₃PO₄

Question 5

What is the charge of Iron in FeO

Answer 5

2+

Question 6

What is the charge of Copper in Cu₂CO₃

Answer 6

1+

Question 7

What is the name of MgS₂O₃

Answer 7

Magnesium thiosulfate (page 8 of databooklet)

Question 8

Name of N₃Br₄

Answer 8

Trinitrogen tetrabromide

Question 9

GFM of MgCl₂

Answer 9

95.5

Question 10

GFM of iron (IV) nitride

Answer 10

iron (IV) nitride

Fe N

4 3

3 4

Fe₃N₄

(3x56)+(4x14) = 224

Question 11

GFM of Oxygen

Answer 11

Oxygen is O₂ and not O alone. Be careful with the diatomic molecules.

So GFM of oxygen is : 16 x 2 = 32

Question 12

What are the 7 diatomic elements?

Answer 12

H₂ N₂ F₂ O₂ I₂ Cl₂ Br₂

Have No Fear Of Ice Cold Beer

Question 13

Calculate the percentage composition of Iron in Fe₂S

Answer 13

GFM= 144

Fe₂ = 112

Percentage of Fe = (112/144) x100 = 77.78%

Question 14

Ammonium nitrate, NH₄NO₃, has a gram formula mass of 80.
Calculate the percentage by mass of nitrogen in ammonium nitrate

Answer 14

There is 2 nitrogen in NH₄NO₃ so mass of nitrogen = 14 x 2 = 28

pecentage by mass of nitrogen = (28/80) x100 = 35%

Question 15

Calculate the concentration of a solution containing 20g of Magnesium in 200cm³ of water.

Answer 15

n= m/ GFM

GFM of magnesium = 24.5

n= 20/24.5 = 0.82 mol

C= n/V

C= 0.82 / 0.2

C= 4.1 mol.l^-1

Question 16

Calculate the number of mole of Potassium in a 4g sample.

Answer 16

n=m/GFM

n=4/24.5

n=0.16 mol