OCR Chemistry A-Level - Modules 1-4
UPDATED Exam Questions and
CORRECT Answers
what is water of crystallisation? - CORRECT ANSWER- water molecules that make up part
of the crystal structure of a solid
define relative isotopic mass - CORRECT ANSWER- the ass of an atom of an isotope of an
el...
what is water of crystallisation? - CORRECT ANSWER- water molecules that make up part
of the crystal structure of a solid
define relative isotopic mass - CORRECT ANSWER- the ass of an atom of an isotope of an
element relative to one twelfth the mass of an atom of C-12
why is relative atomic mass written as a decimal? - CORRECT ANSWER- it is a weighted
average mass
define molecular formula - CORRECT ANSWER- the actual number of atoms of each
element in a compound
define what an orbital is - CORRECT ANSWER- a region within an atom that can hold up to
two electrons of opposite spins
what shape are S orbitals? - CORRECT ANSWER- spherical
what shape are orbitals? - CORRECT ANSWER- figure of 8
how can you make out the electron structure of an element using the periodic table? -
CORRECT ANSWER- period = energy level
columns = electrons
group = subshell
show the oxidation of sodium and the reduction of chlorine - CORRECT ANSWER- Na ->
Na+ + e-
Cl + e- -> Cl-
, ions always go on the RHS whether oxidation or reduction
define ionic bond - CORRECT ANSWER- the electrostatic force of attraction between
positive and negative ions
ionic bonding occurs between metals and non-metals but which ion is the exception? -
CORRECT ANSWER- NH4+
define covalent bond - CORRECT ANSWER- the strong electrostatic force of attraction
between the shared pair of electrons and the nuclei of the bonded atoms
when non-metals covalently bond, what is their aim? - CORRECT ANSWER- the octet rule:
- to reach a noble gas configuration (8 electrons in the outer shell)
what are there exceptions to the octet rule? - CORRECT ANSWER- - NO (odd number of
electrons)
- BF3 (boron has less than 8 outershell electrons)
- SF6 (sulfur has more than 8 outershell electrons)
why can sulfur have more than 8 electrons in its outershell? - CORRECT ANSWER- it has an
empty 3d subshell
define a dative covalent bond - CORRECT ANSWER- a shared pair of electrons which has
been provided by only one of the bonding atoms
give some common examples of ions with a dative bond - CORRECT ANSWER- NH4+
H3O+
what is a base? - CORRECT ANSWER- proton (H+) acceptors
what is the shape of an atom determined by? - CORRECT ANSWER- - the number of
electron pairs
- electron pairs repel to become as far apart as possible
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller MGRADES. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $7.99. You're not tied to anything after your purchase.
