C2.2 Ionic Compounds and Analysis

Question 1

What can atoms of different elements do?

Answer 1

Combine to form compounds by formation of new chemical bonds

Question 2

How are ionic bonds formed and what does it produce?

Answer 2

By the atoms gaining or losing electrons during a chemical reaction

Metal atoms lose electrons to from Cations

Non-metal atoms gain electrons to form negatively charged ions (Anions)

Question 3

What is an ion?

Answer 3

An atom or a group of atoms with an electrical charge ( + or -)

Question 4

Describe the formation of Sodium Ions

Answer 4

The Sodium ion Na+, forms from sodium atoms Na+ sign shows a sodium ion

Chloride atoms Cl become chloride ions Cl-. - sign shows a chloride ion carries a single negative charge

The number of atoms that groups 6 and 7 can gain is 8 minus the group number

Question 5

What does the ending “Ide” and “Ate” show?

Answer 5

Ide ending shows only that element is present

Ate ending shows oxygen atoms are present

Question 6

Describe the formulae of ionic compounds

Answer 6

Negative Ions Charge
Chloride Cl^- 1-
Bromide Br^- 1-
Iodide I^- 1-
Hydroxide OH^- 1-
Nitrates No3^- 1-
Carbonates CO3^-2 2-
Oxides O^2- 2-
Sulfate SO4^2- 2-

Question 7

Describe the structure of ionic compounds as a lattice structure

Answer 7

The Lattice Structure is a regular grid arrangement of particles such as ions

The ions in a Lattice Structure are held by strong electrostatic forces between oppositely charged ions

Question 8

Describe and explain the properties of ionic substances

Answer 8

Ionic substances including sodium chloride and magnesium oxide can:

Conduct electricity when molten and in aqueous solution

Have high melting and boiling points

Doesn’t conduct electricity when sold

Question 9

Describe the general rules that describe the solubility of common types of substances in water

Answer 9

Soluble in Water:
All common sodium, potassium and ammonium salts
All nitrates
Most Chlorides
Most Sulfates
Sodium Carbonate, Potassium and Ammonium Carbonate
Sodium, Potassium and Ammonium Hydroxide

Insoluble in Water:
Silver Chloride Lead
Lead, Barium and Calcium Sulfate
Most Carbonates
Most Hydroxides

Question 10

What can insoluble salts be formed as?

Answer 10

Precipitates by the reaction of suitable reagents in solution

Question 11

Why is the insoluble salt, Barium Sulfate given as a Barium Meal to X-Ray patients?

Answer 11

1. Only bones normally show up in a X-Ray
2. Barium Sulfate is opaque to X-Rays. The gut shows up when drunk so any problems can be seen
3. Barium salts are toxic but Barium Sulfate can be safely drunk because it’s insoluble (Not absorbed in the blood stream - it just passes through the body)
4. When a patient drinks Barium Sulfate before X-Ray, it’s known as a Barium Meal

Question 12

Describe the tests for Metal/Positive ions

Answer 12

Flame Test:
Metals change the colour of a flame when they are heated in it
1. Dip a clean flame test loop in the sample solution
2. Hold the flame test loop at the edge of a Bunsen Burner flame
3. Observe the changed colour of the flame and decide which metal it indicates
4. Clean the loop in concentrated acid and rinse with water then repeat steps 1 to 3 with a new sample

Question 13

Describe the tests for Non-Metal/Negative ions

Answer 13

Carbonate ion:

1. Add dilute acid
2. If Carbonate ions are present, Carbon Dioxide gas passes bubbles through limewater
3. Limewater goes cloudy and milky

Sulphate ion:

1. Add a few drops of dilute HCL to the solution
2. Add a few drops of Barium Chloride Solution
3. White Precipitate forms if Sulphate ions are present

Chloride:

1. Add a few drops of dilute Nitric acid to the sample solution where it’s shaken
2. Add Silver Nitrate solution
3. White Precipitate forms is Chloride ions are present