Exam Questions Flashcards
Define the term isotomic mass
The mass of an atom compared to 1/12th of C12
What does ‘.xH2O’ represent?
Water of crystalisation
Define the term atomic mass
It is the mean mass of an atom compared to 1/12th of carbon 12
Define the term ionic bonding
The electrostatci attraction between oppositely charaged ions
What is ment by the term isotopes?
Atoms of an element with different numbers of neutrons
Different isotopes of antimony have the same chemical propertu. Explain why.
They have the same number of electrons in their outmost shell
Define the term relative atomic mass
It is the mean mass of an atom compaired to 1/12th of carbon 12
What is meant by an orbital?
A region that can hold two electrons
State the total number of electrons occupying the p orbitals in one chlorine atom
11
Explain why xenon has a lower firs ionisation energy than neon
Xeon has more shells and more shielding. The nucleus attraction decreases
Explain why xenon has a lower first ionisation energy than neon
Xeon has more shells and more shielding. The nucleus attraction decreases
What is the relative mass of an electron?
1/1836
Define the term relative isotopic mass
The mass of an atom compared to 1/12th of C12
What is meant by one mole of a substance?
The amount of substance which contains as many particles as there are carbon atoms in 12g of carbon-12
Predict the shape and bond angle of lead in lead tetraethyl, explain your answer.
Shape: Tetrahedral
Bond angle: 109o
Explanation: It has four sets of electrons, which repel as far from each other as possible
Why is Na3PO4 described as a salt of H3PO4?
The H+ ions are replaced by sodium ions
What are the main intermolecular forces in NH3?
Hydrogen bonding
What are the main intermolecular forces in PH3?
Permanent dipole
What is a dative covalent bond?
Both electrons have been dnated by 1 atom
What is the bond angle of F-B-F in BF3?
120o
What is the bond angle of F-B-F in H3NBF3?
109.5o
The H-N-H bond angle in NH3 is 107o. A student predicted the the H-N-H bond angle in H3NBF is larger.
Explain why the student may have expected the H-N-H bond angle to be larger in H3NBF3 than in NH3
N in NH3 has 3 bonding pairs and 1 lone pair of electrons
N in H3NBF3 has 4 bonding pairs of electrons
Lone pair of electrons repel more than bonding pairs
State the shape of a molecule of SF6
Octahedral
Molecules of BF3 contain polar bonds, but the molecules are non-polar, why?
BF3 is symmetrical and therefore the dipoles cancel out
What si the shape of a molecule of SbCl3 and why?
Shape: Trigonal pyramid
Explanation: Sb has 3 bonding prais and 1 lone pair of electrons. Pairs of electrons repel
Why is SbCl3 polar?
There is difference of electronegativity and the dipoles don’t cancel out
What are the formulae of the ions present in the salt, H4N2O3?
NH4+ and NO3-
State 2 examples of anomalous properties of ice caused by Hydrogen bonding
Ice is less dense than water - molecules of ice are held by H-bonds
Ice has a relatively high melting point - H-bonds relatively strong
Explain why lithium fluoride conducts electricity when molten but not when solid
Ions cannot move in solids but they can when in molten
Fluorine reacts with boron, B, to form the fluoride BF3. Suggest an equation for this reaction
2B + 3F2 —> 2BF3
Name the shape of, and state the bond angles in, a BF3 molecule. Explain why BF3 has this shape
Shape: Trigonal planar
Angle: 120o
Explanation: The pairs of electrons repel. Boron has 3 bonded pairs
Explain why NF3 has a permanent dipole
F is more electronegative than N
Dipoles don’t cancel
In terms of protons, neutrons and electrons, how is an atom of 151Eu different from an atom of 153Eu?
153 has to more neutrons
In terms of protons, neutrons and electrons, how is an atom of 151Eu similar from an atom of 153Eu?
Same number of protons and electrons
Why is calcium nitrate an example of a salt?
The H+ ions in a nitric acid has been replaced by calcium ions
Explain how the hydroxide ion in aqueous calcium hydroxide acts as a base when it neutralises dilute nitric acid
Accepts a proton
Predict the bond angle in an F2O molecule, explain your anser
BOnd angle: 104 -105
Explanation: There are 2 bonded pairs and 2 lone paira. The lone apris repal more than the bonded pairs
What term is used to describe a redox reaction in which an element is both oxidised and reduced?
Disproportional
Name the shape of a molecule of CH3Cl
Tetrahedral
Explain why ZnCl2 is a salt
H+ ions are replaced by zinc ions
What is meant by the term hydrated calcium chloride?
Contains water of crystallisation
How many full orbitals are an atom of sulfur?
7
Why can ammonium be described as a salt?
The H+ ions have been replaced by ammonium ion
