Chem Revision Flashcards
1 mark per MCQ
Which one of the following corresponds to the configuration of the three electrons of highest energy for the ground state of an element in Group 13?
Option A: 1s^2 2s^1
Option B: 3s^1 3p^2
Option C: 2s^2 2p^1
Option D: 3p^3
Option B.
A is Group 1, D is Group 15
Some isotopes are unstable and decompose naturally. In one type of decomposition, a neutron in the nucleus is converted into a proton, which is retained in the nucleus, and an electron, which is expelled from the atom.
Which change describes the process above?
Option A: ^11 C -> ^12 C
Option B: ^32 P -> ^31 P
Option C: ^22 Na -> ^22 Ne
Option D: ^40 K -> ^40 Ca
Option D.
Different proton number: different element
(multiple select) Which of the statements are correct?
Option A: Potassium chloride has a higher melting point than calcium chloride as the potassium ion has a greater charge than the calcium ion.
Option B: In the calcium chloride lattice, the ratio of calcium ions to chloride ions is half of the ratio of potassium ions to chloride ions in the potassium chloride lattice.
Option C: Molten calcium chloride has a greater electrical conductivity than molten potassium chloride as calcium contributes more electrons to the delocalise “sea of electrons” than does potassium.
Option B only.
Option B the ratio is 1:2 and 2:2, it is half.
Option C: Not metals, ionic compounds do not have delocalised sea of electrons
Which one of the following corresponds to the configuration of the four electrons of highest energy for the ground state of an element in Group 14?
Option A: 1s^2 2s^1 2p^1
Option B: 1s^2 2s^2
Option C: 2s^2 2p^2
Option D: 3p^4
Option C
Higher quantum number: greater energy, thus Option B is rejected.
State, and explain in terms of structure and bonding, how the electrical conductivity of lithium chloride varies in different states. [3]
LiCl exists as Li+ and Cl- ions held together in a giant ionic lattice with strong electrostatic forces of attraction, holding them in fixed positions. LiCl does not conduct electricity in the solid state as the oppositely charged ions are not free to move, thus no mobile ions to act as charge carriers. LiCl conducts electricity in the molten and aqueous state. The ionic lattice is broken down and the ions are free to move about their positions. They flow towards the oppositely charged electrodes and act as mobile charge carriers, carrying a current.
Describe the structure and bonding of tin (Sn^2+). [2]
The structure of tin consists of tin ions held in a giant metallic lattice in a sea of delocalised electrons. Metallic bonding exists with electrostatic forces of attraction between the tin ions and the sea of delocalised electrons.
The main component of sapphires is aluminium oxide.
Explain, in terms of structure and bonding, the hardness of sapphires at room temperature. [2]
Sapphire has a giant ionic lattice and the oppositely charged ions are held in fixed positions by the strong electrostatic forces of attraction. At room temperature, there is insufficient energy to overcome these strong electrostatic forces of attraction and break the lattice structure.
Explain why argon does not form an oxide. [1]
The valence shell of argon is fully filled / Argon has attained the noble gas electronic configuration / octet structure. It is stable and will not gain, lose, or share electrons to form an oxide.
State the function of a locating agent in a chromatography experiment. [1]
To react with colourless substances and produce coloured products / spots.
a) Draw the electron-in-box diagram for hydrogen atom and chlorine atom respectively. [2]
b) Sketch the shapes of the orbitals in the valence shell of chlorine atom. [2]
c) In the formation of the
H-Cl bond, the orbitals containing the valence electrons of H and Cl atoms overlap.
From (a), state the orbitals that overlap in the H-Cl bond. [1]
H:
Cl:
d) Draw the shapes of the orbitals that overlap in the
H-Cl bond. Label the orbitals with the subshells that they belong in. [1]
a) For chlorine atom, 1s, 2s, 2p, 3s are completely filled, 5 electrons in 3p
b) 3s, 3px, 3py, 3pz
c) H: 1s
Cl: 3p
d) 1s overlapping with 3p
A student carried out paper chromatography, using ethanol-water solvent on a sample. The sample was found to have a spot on the start line of the chromatogram.
The student concluded that the sample is a pure substance. Explain if you agree with this statement. [1]
I disagree. The sample did not separate out into spots as it is insoluble in the ethanol-water solvent. [0.5]
Hence, it cannot be concluded that the sample has only 1 spot. / the sample may have more than 1 spot. [0.5]
The relative abundance of 63Cu and 65Cu are 69.15% and 30.85% respectively. Calculate the relative atomic mass of copper. [1]
63.6 (to 3s.f.)
- write statement!
Why does hydrogen chloride gas not have an effect on dry litmus paper?
Hydrogen chloride has a simple molecular structure and does not ionise into H^+ and Cl^- ions in the absence of water.
