2015 Atoms, Bonds and Groups

Question 1

State what is meant by the term empirical formula

Answer 1

The simplest whole number ratio of atoms (of each element) present in a compound

Question 2

Describe what is meant by the term ionic lattice, in terms of the type and arrangement of particles present

Answer 2

Repeating pattern of oppositely charged ions

Question 3

What is meant by a covalent bond

Answer 3

• A shared pair of electrons

Question 4

Explain what is meant by the term electronegativity

Answer 4

• The ability of an atom to attract electrons

* Electron pair in a covalent bond

Question 5

A student bubbles chlorine gas through aqueous potassium iodide . A reaction takes place

State what the student would observe

Answer 5

• The solution would turn yellow OR orange OR brown

Question 6

Explain what is meant by the terms base and alkali

Answer 6

Base
• A substance which readily accepts H ions from an acid
Alkali
• Releases OH ions into aqueous solution

Question 7

A student prepared some calcium hydroxide by adding a small piece of calcium to a large excess of water

Describe what the student would observe and write the equation for the reaction

Answer 7

Observation
• Effervescence OR fizzing OR bubbling OR gas produced
• The solid OR calcium OR the metal would dissolve OR
disappear OR a (colourless) solution forms 

Ca + 2H2O > Ca(OH)2 + H2

Question 8

Explain why a CH2Cl2 molecule is polar

Answer 8

• The dipoles do not cancel out

* Because the molecule is non-symmetrical

Question 9

A student prepares a solution of calcium nitrate from calcium carbonate
What reagent would the student use

Answer 9

• Nitric acid OR HNO3

* CaCO3 + 2HNO3  Ca(NO3)2 + H2O + CO2

Question 10

State how and explain why the attraction between nuclei and outermost electrons in gaseous atoms varies across Period 3

Answer 10

• The attraction (between nuclei and outermost electrons)
increases (across the period)
• The nuclear charge increases/number of protons increases
• Outer electrons are in the same shell/(Outer) electrons experience similar shielding/Same number of shells/Atomic radius decreases

Question 11

The table shows the boiling points of ammonia, fluorine and bromine Ammonia NH3 -33
Fluorine F2 -188
Bromine Br2 59
Explain the different boiling points of NH3, F2 and Br2

Answer 11

• NH3 has hydrogen bonding
• F2 AND Br2 have induced dipole temporary
• Forces are intermolecular for ammonia
• Forces are intermolecular for fluorine OR for bromine
• The induced dipoles in Br2 are greater than in F2
because bromine has more electrons than fluorine
• The induced dipoles in Br2 are greater than
hydrogen bonding in NH3 and the hydrogen bonding in NH3 is stronger than induced dipoles in F2

Question 12

Cerium behaves as a typical metal when it reacts with dilute sulphuric acid to form a salt. What is the second product of this reaction

Answer 12

• Hydrogen

Question 13

How has a salt been formed in this reaction.

Answer 13

• A hydrogen ion (of an acid) has been replaced by a metal ion

Question 14

State whether these substances conduct electricity when solid or molten
• Aluminium
• Aluminium fluoride
• Boron tribromide

Answer 14

Aluminium
• Aluminium conducts in solid and molten states
• Aluminium has delocalised electrons
Aluminium flouride
• Aluminium fluoride conducts when molten because it has mobile ions
• Solid aluminium fluoride has ions which are fixed (in
position
• In an (ionic) lattice
Boron tribromide
• Boron tribromide does not conduct in solid and molten
states
• Boron tribromide has no mobile electrons OR no (mobile) ions