chap 3 4 5 chem test

Question 1

What is the chemical formula for barium sulphate?

Answer 1

BaSO4

Question 2

What is the shape for methane CH4

Answer 2

Tetrahedral

Question 3

Use methane to describe the difference between the intermolecular and intramolecular forces?

Answer 3

Intermolecular forces:
- Electrostatic force of attraction between molecules including dipole-dipole forces, hydrogen bonds and dispersion forces.
Intramolecular forces:
- A force that holds the atoms within a molecule together

Methane is a covalent non-polar compound, meaning it cannot conduct electricity or heat. Collisions between methane molecules become more frequent and energy is transferred from one molecule to another. However in metals, they allow the electrons to move more freely, the energy is not transferred from one atom to another. They absorb the energy and move around more rapidly, creating heat. Covalent compounds like methane are poor conductors due to their tightly bound electrons.

Question 4

Name the positive ion in magnesium ribbon

Answer 4

Mg2+

Question 5

What is the ratio of metal ions to delocalised electrons in magnesium ribbon? Justify your answer

Answer 5

Each magnesium atom releases 2 valence electrons to form delocalised electrons that move freely throughout the metal lattice. The magnesium atoms then become positively charged ions, each with a 2+ charge, since they have lost 2 negatively charged electrons. Therefore, the ratio is 1:2

Question 6

Use bonding models to explain the property in ionic compounds can conduct electricity in molten and aqueous state but not solid state

Answer 6

In solid state, the atoms form ions that are held together by strong electrostatic attraction between oppositely charged ions. In a solid ionic compound, these ions are arranged in a lattice, which means that ions are held in a fixed position and unable to move freely.

Question 7

Use bonding models to explain the property in covalent compounds conduct less electricity

Answer 7

Covalent compounds conduct less electricity because they do not contain free ions that can move & carry an electricity charge. The electrons are shared between atoms to form molecular orbitals, and these electrons are not free to move around.

Question 8

Use bonding models to explain the property in metallic compounds are malleable and ductile

Answer 8

Metallic componds are composed of metal atoms that form a lattice structure in which the outermost elecrtrons of each metal atom are delocalised and from a sea of electrons that are free to move throughout the metal lattice. These allow the metal to be reshaped without breaking.

Question 9

Which molecules exhibit dipole-dipole forces?

Answer 9

Polar molecules

Question 10

What examples of polar molecules are there?

Answer 10

Water, ammonia and sulfur dioxide