Mini guide to chemistry AS OCR Spec A

1. THE MINI
DEFINITIVE
CHEMISTRY GUIDE
Disclaimer: May not be that definitive,
calculator may be needed for some of
the questions.
Definition Ion Question
Equations
s formulae s

2. GLOSSARY
Avagadro’s Constant Waters of Proton Number
Crystallisation
Molar Mass Relative isotopic mass
Combustion
Amount of Substance Relative atomic mass
Acid
Mole Mass spectrum of element
Alkali
Empirical Formula Valency (not required for
Base exam)
Molecular Formula
1st Ionisation Energy Isotope
Anhydrous
2nd Ionisation Energy
Hydrated
Orbital

3. AVAGADRO’S CONSTANT
 The number of particles in a mole. (6.02x1023)
MOLAR MASS
 The mass per mole of a substance (gmol-1)
AMOUNT OF SUBSTANCE
 The quantity who’s unit is the mole (mol)
Back to
glossary

4. MOLE
 The amount of any substance containing the same amount of
particles as there are carbon atoms in 12 grams of carbon 12
isotope.
EMPIRICAL FORMULA
 The simplest whole number ratio of atoms of each element in a
compound.
MOLECULAR FORMULA
 The actual number of atoms of each element in a molecule.
Back to
glossary

5. ANHYDROUS
 A substance that contains no water molecules
HYDRATED
 A crystalline compound that contains water molecules
WATERS OF CRYSTALLISATION
 Water molecules that form part of the crystalline structure of the
compound
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glossary

6. COMBUSTION
 When a substance reacts with O2 to form its oxides.
ACID
 A proton donor (H+)
ALKALI
 A substance that dissolves in water to release OH- ions
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glossary

7. BASE
 A proton receiver (H+)
1ST IONISATION ENERGY
 The amount of energy required to remove 1 mole of electrons
from 1 mole of gaseous atoms
2ND IONISATION ENERGY
 The amount of energy required to remove 1 mole of electrons
from 1 mole of gaseous +1 ions
Back to
glossary

8. ORBITAL
 A region of space that holds up to 2 electrons with opposite spins
PROTON NUMBER
 The number of protons in the nucleus
RELATIVE ISOTOPIC MASS
 The mass of an atom of an isotope relative to 1/12 of carbon-12
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glossary

9. MASS SPECTRUM OF AN ELEMENT
 … Shows the relative isotopic mass of each isotope of an element
and their abundance
RELATIVE ATOMIC MASS
 The weighted mean mass of an element relative to 1/12 of carbon
12
VALENCY (NOT REQUIRED FOR
EXAM)
 The number of atoms an atom has the affinity to bond with. In
other words the amount of holes in an atom in a modelling kit. to
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glossary

10. ISOTOPE
 Contains the same number of protons (and electrons) but different
number of neutrons.
Back to
glossary

11. EQUATIONS
 Mass = Moles * Molar mass (Mr) (mass g, moles mol, Mr gmol-1)
 Gdm-3 = Mol dm-3 * Mr (Gdm-3 and mol dm-3 = ditto, Mr gmol-1)
 Moles = Concentration * Volume (Moles, mol Concentration gmol-
1 or mol dm-3 , Volume = dm3
 Volume = Moles * 24 (volume dm3, moles mol, 24 = dm3 mol-1)
 Acid + Alkali  Salt + Water
 Metal oxide + Acid  Salt + Water
 Metal + Acid  Salt + H2
 Ammonia (NH3)+ Acid  Salt
 Carbonate + Acid  Salt + Water + CO2

12. COMMON ION FORMULAE
-2 -3
+/-1
 Ammonium = NH4+  Sulphate = SO42-  Phosphate PO43-
 Hydroxide = OH-  Sulphide = S2-
 Nitride N3-
 Nitrate = NO3-  Oxide = O2-
 Hydrogen carbonate HCO3- Carbonate = CO32-


13. 1) What is the definition for “1st ionisation energy”?
Reveal answer
 The amount of energy required to remove 1 mole of electrons
from 1 mole of gaseous atoms
2) When given moles and concentration, how do you calculate
volume? Reveal answer
 Moles = Conc * Vol, so Vol = Mol / Conc
3) What is the valency of carbon?
Reveal answer
 4. It is a sneaky question, but think back to biology lessons with
the modelling kits ;)
Next set of questions Remember
score out
of 3 for
later

14. 4) When given 24 and moles, what can you calculate? (and
how?)
Reveal answer
 Moles * 24 = Volume. (Only for gasses at RTP)
5) What is the definition of “waters of crystallisation”
Reveal answer
 Water molecules that form part of the crystalline structure of the
compound
6) As well as the obvious difference of “contains water molecules” and
“contains no water molecules”, what is the difference between
“anhydrous” and “hydrated”? (recite definitions mentally)
Reveal answer
 Ouch, tough one. Remember “an” meaning “exempt”? So an
anhydrous substance is “exempt” from being a crystalline
molecule.
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6)

15. 7) What are the ionic formulae (with charges) for Nitrate +
Nitride?
Reveal answer
 Nitrate = NO3-
 Nitride N3-
8) What is the definition of “Alkali”?
Reveal answer
 A substance that dissolves in water to release OH- ions
9) Calculate the volume of 15 g dm-3 calcium chloride
required to give 0.150 moles. (hint, you need 2 triangles)
Reveal answer
 1.10 dm3. Follow THIS LINK for the workings.
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9)

16. WORKED QUESTION 9
 First write out the chemical formula. CaCl2. (Remember ionic
charge)
 You have been given the g dm-3. You need 2 numbers to use any
of the 4 triangles. So what else can you work out from the
question?
 The Mr of the compound! (which is 40.1 + 35.5*2)
 G dm-3 divided by Mr gives mol dm-3. (0.135)
 So how can you calculate volume from mol dm-3? Well split up
mol and dm3. You have 1 dm3, and 0.135 0.135 The question
3
moles.
Use
same
asks 1 dm many dm3 make 0.15 moles. So moles of it this way…to 0.150
how think From 0.135
= *by 1.1 recurring.
number (click anywhere to cont) (0.150 / 0.135. New
(multiply 0.150 over old.)
1 by 1.1 Answer moles
recurring
) Back to Q9

17. 10) What is the definition for “orbital”?
Reveal answer
 A region of space that holds up to 2 electrons with opposite spins
11) What is the definition for “Isotope?”
Reveal answer
 Contains the same number of protons (and electrons) but different
number of neutrons.
12) What mass of MgO is formed by the complete
combustion of 24 g of Magnesium
Reveal answer
 First balance the equation to get 2Mg + O2  2 MgO
 You have 24 g of magnesium. You need the moles. 24 / 24.3 = 0.987… mol
 0.987 * (24.3 + 16) = 39.8 g
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12)

18. 13) Metal + Acid  What?
Reveal answer
 Salt + Hydrogen gas
14) Metal oxide + Acid  what?
Reveal answer
 Salt + Water. Logical as the only difference is the insertion of a
water molecule into the metal.
15) What is the definition of “Empirical Formula”?
Reveal answer
 The simplest whole number ratio of atoms of each element in a
compound.
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15)

19. 16) What is the definition of “molar mass”?
Reveal answer
 The quantity (of a substance) who’s unit is the mole
17) When 14.2 g of hydrated nickel (11) nitrate is dried, 8.9 g
remains. Find x in Ni(NO3)2 . X H2O
Reveal answer
 X = 6. Find the mass of water, and of nickel nitrate. Then use
mass = moles * Mr to find the moles. Divide both by smallest
18) What are x. ionic formulae for a) carbonate b)
moles to get the
hydrogen carbonate?
Reveal answer
 Carbonate = CO3 2-
 Hydrogen Carbonate = HCO3-
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20. 19) What is the definition of “mole”?
Reveal answer
 The amount of any substance containing the same amount of
particles as there are carbon atoms in 12 grams of carbon 12
isotope.
20) What is the definition of “relative isotopic mass?”
Reveal answer
 The mass of an atom of an isotope relative to 1/12 of carbon-12
21) X + Acid  Salt + Water + CO2
Reveal answer
 Carbonate.
Next Continue…
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21)

21. THE MOMENT OF TRUTH, YOUR
SCORE…
90% +
 Fantastic!
A*
80% +
 Great!
A
70% +
…
B
60% +
 Never!
C