1.1 - Formulae and equations

Question 1

What is the formula for:

Sulfur dioxide
Methane
Hydrochloric acid
Sulfuric acid
Nitric acid
Ethanoic acid
Ammonia
Ammonium chloride

Answer 1

SO2
CH4
HCL
H2SO4
NHO3
CH3COOH
NH3
NH4CL

Question 2

What is the formula for:

Sodium hydroxide
Sodium chloride
Sodium carbonate
Sodium hydrogen-carbonate
Sodium sulfate
Copper (II) oxide
Copper (II) sulfate
Calcium hydroxide
Calcium carbonate
Calcium chloride

Answer 2

NaOH
NaCl
NA2CO3
NAHCO3
Na2SO4
CuO
CuSO4
Ca(OH)2
CaCO3
CaCl2

Question 3

What are the formula for these ions:

Ammonium
Hydrogen
Lithium
Potassium
Sodium
Silver
Barium
Calcium
Magnesium
Copper (II)
Iron (II)
Iron (III)
Aluminium

Answer 3

NH4+
H+
Li+
K+
Na+
Ag+
Ba2+
Ca2+
Mg2+
Cu2+
Fe2+
Fe3+
Al3+

Question 4

What are the formula for these ions:

Bromide
Chloride
Fluoride
Iodide
Hydrogencarbonate
Hydroxide
Nitrate
Oxide
Sulfide
Carbonate
Sulfate
Phosphate

Answer 4

Br-
Cl-
F-
I-
HCO3-
OH-
NO3-
02-
S2-
CO3,2-
SO4,2-
PO4,3-

Question 5

How do you calculate the formula for an ionic compound?

Answer 5

Balance the ions so that the total of the positive ions (cations) and negative ions (anions) adds to 0

Question 6

What the ionic formula for Sodium Sulfide?

Answer 6

1. Ions are Na+ AND S2-
2. to make total charge zero, need two Na+ ions for every S2
3. Na2S

Question 7

What is an oxidation number?

Answer 7

Is the number of electrons that need to be added to (or taken away from) an element to make it neutral

Question 8

Iron(II) ion, Fe2+, needs the addition of ___ electrons to make it a neutral atom, therefore it has the oxidation number of __
Cl- needs to loose __ electron –> neutral, therefore its oxidation number = __

Answer 8

2
+2
1
-1

Question 9

What are the rules of oxidation numbers?

Answer 9

ON of uncombined element = 0
sum of ON in compound = 0
sum of ON’s in an ion = overall charge
ON of group 1 =+1, group 2 = +2, group 6 = -2, group 7 = -1
ON of Oxygen is -2 unless when bonded to Fluorine or peroxides (H202, O=-1)(OF2, O=+2)
ON of Hydrogen = +1 except when bonded to group 1 or 2 (NaH, H=1)
In chemical species with atoms of more that one element, the most electronegative element is given the negative oxidation number

Question 10

Oxidation numbers are used in _____ reactions to show which species is oxidised and which one is reduced, if the ON of species increases —> its ________. If the ON decreases —–> it is _______

Answer 10

redox
oxidised
reduced

Question 11

ON numbers can be used to name compounds. E.g. Potassium, N and O can combine to give 2 different compounds, KNO3 and KNO2. Since the oxidation number of potassium is +1 and that of Oxygen -2, the oxidation number of nitrogen must be +5 IN KNO3 and +3 in KNO2. Therefore KNO3 is called potassium nitrate(V) and KNO2 is called potassium nitrate (III)

Answer 11

Understand?

Question 12

What are the steps in writing a balanced chemical equation?

Answer 12

1. Write a word equation for the reaction
2. Write symbols and formula for the reactants and products
3. Balance equation by multiplying formula if necessary
4. Add state symbols

Question 13

What are the state symbols for:
solid
gas
liquid
solution in water

Answer 13

s
g
l
aq

Question 14

Name some diatomic molecules

Answer 14

O, H, Br, I, N, Cl

Question 15

Example of Ionic equation:

When a solution of sodium hydroxide is added to a solution of magnesium chloride a white prec forms

The chemical equation of the reaction is:

2NaOH(aq) + MgCl2(aq) —> 2NaCl(aq) + Mg(OH)2(s)

Writing out all the ions gives:
2Na+(aq) + 2OH-(aq) + Mg2+(aq) + 2Cl-(aq) —> 2Na+(aq) + 2Cl-(aq) + Mg(Oh)2(s)

The Na+ ions and the Cl- ions do not change during the reaction. They’re spectator ions and can be omitted, giving the ionic equation:
Mg2+(aq) + 2OH-(aq) —> Mg(OH)2(s)

Answer 15

Understand?