2012 Atoms, Bonds and Groups Jan

Question 1

Define relative isotopic mass

Answer 1

• Mass of an atom of an isotope compared to 1/12th

* (The mass of a) 12C (atom)

Question 2

When clorine is bubbled through the aqueous solution of potassium iodide. Ionic equation

Answer 2

• Cl2 + 2I– -> 2Cl– + I2

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Question 3

Explain in terms of intermolecular forces present, why ICl has a higher boiling point than Cl2

Answer 3

• ICl has permanent dipole (–dipole) (interactions) AND
Cl2 has (only) induced
• ICl has more electrons
• More energy is needed to overcome forces in ICl 

Question 4

Describe a chemical test which the student could have carrried out to prove that the filtrate contains chloride ions

Answer 4

• Add (aqueous) silver nitrate

* White AND precipitate

Question 5

What is meant by hydrated calcium chloride

Answer 5

• Contains water (of crystallisation)

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Question 6

What is meant by an orbital

Answer 6

• A region (within an atom) that can hold (up to) two
electrons  (with opposite spin)
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Question 7

What is meant by one mole of a substance

Answer 7

• (The amount of substance which contains) as many
particles as there are carbon atoms in 12g of 12C (atoms)
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Question 8

Define first ionisation energy

Answer 8

• Energy (needed) to remove an electron
• From each atom in one mole
• Of gaseous atoms

Question 9

Explain why there is an increase in first ionisation energy between Fe and Ne

Answer 9

From F to Ne
• Nuclear charge increases
• (Outermost) electrons experience the same shielding
• Greater nuclear attraction

Question 10

Explain why there is a decrease in first ionisation energy between Ne and Na

Answer 10

From Ne to Na
• Na has more shells
• Outermost) electron experiences greater shielding
• Less nuclear attraction

Question 11

Explain why there is a difference in melting points of K, KBr and H2O

Answer 11

• In K, (electrostatic attraction between)
positive ions AND electrons
• In KBr, (electrostatic attraction between) positively AND
• Negatively charged ions
• K has metallic bonding
• KBr has ionic bonding
• Hydrogen bonding IN H2O between molecules
• Ionic bonding > metallic bonding > hydrogen bonding

Question 12

Predict the bond angle in H-N-H in hydrazine molecule

Answer 12

• Predicted bond angle 107
• There are 3 bonded pairs and 1 lone pair
• Electron pairs repel
• Lone pairs repel more than bonded pairs

Question 13

What is the name for NaClO

Answer 13

• Sodium chlorate(I)