Friday, March 17, 2017

C2 Chemistry of Elements All Specification Notes

Groups and periods in the periodic table

Group are the columns. Group number = number of electrons in the outermost shell
Periods are the rows. Row number = number of orbitals the atom has
Metals and nonmetals in the periodic table
Hydrogen is also a metal.
Remember that the big one is the metals.

The satire lies below BSATA.
Metal oxides property

Metals – conductors, form metal oxides which are alkaline
Non-metals – non conductors, forms non-metal oxides which are acidic
Why elements in the same group have similar properties

They have the same number of electrons in the outermost shell (valence electrons) hence they make similar kind of bonds with other atoms.
Noble gases

All the noble gases in group 0 are inert and they are very unreactive because they have a full outer electron shell which means they are stable.
Group 1 elements reaction with water

Group one elements react vigorously with water. They produce hydrogen gas and metal hydroxide.
Relative reactivity of group one elements

The reactivity of group one elements decreases as we go down the group.

Francium is the most reactive followed by cesium, rubidium, potassium, sodium, lithium.
Relative reactivity of group one elements in terms of the distance between outer electrons and the nucleus

The reactivity increases as we go further down the group. Further down the group, there are more electron shells hence making the outer shell further away from the nucleus. The further the outer shell is from the nucleus, the weaker is the attraction force between nucleus and the outer shell electrons as positive nucleus attracts negatively charged electrons. The weaker force therefore, makes the atom easier to lose the outer shell electrons hence making theme more reactive.

Halogens colors and physical state at room temperature

Color (room temp)
State (room temp)
Molecular Formula
Shiny purple (silver)
Properties of other halogen pattern

Further down the group the boiling and melting point keep increasing and the color also get darker.
Hydrogen chloride vs hydrochloric acid

Hydrogen chloride is colorless gas at room temperature and it is not acidic.

However hydrochloric acid is a solution of hydrogen chloride gas and it is acidic. When made into a solution in water, the H+ and Cl- ions in hydrogen chloride separate. The H+ ions give hydrochloric acid its acidity.
Why hydrogen chloride is only acidic in water but not in methylbenzene

Hydrogen chloride gas is insoluble in methylbenzene as it is a non-polar molecule hence it does not dissolve in it and does not cause the dissociation between the H+ and Cl- ions. But hydrogen chloride is soluble in water as it is a polar molecule hence breaking the bond between the H+ and Cl- ions and causing dissociation and the acidity as H+ ions on their own are acidic.
Relative reactivity of group one elements

Halogens get more reactive as we go further up the group.

Fluorine is the most reactive followed by, chlorine, bromine, iodine and astatine.
Experiment to show a more reactive halogen will displace a less reactive one

Take a test tube with potassium bromide solution and mix it with some chlorine gas.  

The gases present in the air

Nitrogen - 78%
Oxygen - 21%
Other (argon, water vapour, carbon dioxide) - 1%

Depending on the air conditions, air may have pollutants and more water vapour.  
Explain experiment involving reaction of elements like iron, copper and phosphorus can be used to determine the percentage of oxygen in air by volume

Phosphorus, iron and phosphorus can be reacted with air. We can put enough of these elements in a airtight chamber with some air and note down the volume of air after and before they reacted with the air.

The volume of air that decreased after the reaction should be all oxygen. So we can use this formula to work out the percentage of the oxygen in that air.

oxygen% = volume of air before reaction/difference in volume after reaction x 100
Describe experiment to prepare oxygen in lab using hydrogen peroxide and manganese oxide

  • Take a conical flask and fill it with hydrogen peroxide
  • Take a tub full of water and and put a test tube filled with water upside in the tub as such that if a gas is bubbled into the test tube it can displace the water without escaping
  • Add some manganese oxide in the conical flask with hydrogen peroxide and mix it a bit by gently swirling it around.
  • Quickly seal the conical flask with bung which has a delivery tube and bubble the gas produced in the upside down test tube in the tub.

Hydrogen peroxide -> water + oxygen

A diagram is really important for explain this practical

The gas collected can be tested if it is oxygen by the relighting glowing splint test
Reactions of carbon, sulfur and magnesium with air and their acid/base properties

Magnesium is metal. It reacts with air forming a bright white flame. It form a metal-oxide which are basic.

Sulfur and carbon are non-metals. Sulfur reacts with air forming a very small blue flame. Carbon form a yellow-orange flames. Both of these will form non-metal oxides which are acidic.
Experiment to make carbon dioxide in lab

Calcium carbonate can be reacted with hydrochloric acid to produce carbon dioxide. This is a neutralization reaction.

Calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide

  • This is very similar to making oxygen in 2.18
  • Take a conical flask and put in some calcium carbonate and hydrochloric acid
  • These will react and produce carbon dioxide which can be collected using the delivery tube system which displaces water in a upside down testtube

You may test to see if the gas is carbon dioxide by bubbling it through limewater to see if it turn cloudy. If it does, the gas is carbon dioxide.
Formation of carbon dioxide from thermal decomposition of metal carbonates

We can thermally decompose metal carbonates like copper copper carbonate to produce carbon dioxide gas.

Copper carbonate → copper oxide + carbon dioxide
(metal carbonate) → (metal oxide) + (carbon dioxide)

This can be simply done by heating the metal carbonate in a boiling tube over a bunsen burner.

The gas can be collected with a delivery tube attached with bung.
Properties of carbon dioxide gas

  • Colorless
  • Slightly soluble in water, produces a slightly acidic solution when dissolved in water
  • Denser than air
  • Extinguishes flames
  • Turn lime water cloudy
Uses of carbon dioxide

  • Fire extinguishers
    • It is denser than air and does not supports combustion hence it covers the flame and cuts down the supply of oxygen, extinguishing the flame
  • Fizzy drinks
    • Slightly soluble in water so it can be mixed into drinks to make them fizzy
Carbon dioxide as a greenhouse gas

Carbon dioxide is a greenhouse gas as it can absorb and re-emit sun's heat. This may cause it to contribute to climate change is it can make the planet warmer by absorbing heat.
Reaction of metals hydrochloric and sulfuric acid

(metal) + (acid) → (salt) + (hydrogen)
Remember it like MASH

Magnesium – reacts very fast with the acids
Zinc – fizzes fast with the acids
Iron – fizzes slow with the acid
Aluminum – very very slow reaction, releases some bubbles

Combustion of hydrogen

Hydrogen reacts with oxygen and burns rapidly with bright flame. A lot of heat energy is released. Water is released as hydrogen burns.

2H2 + O2 → 2H2O
Using anhydrous copper(II) sulfate as a chemical test for water

Anhydrous copper(II) sulfate will turn from white to blue if it comes in contact with water. This can be used as a test to detect water.

Physical test for finding out if water is pure

We can test the boiling and freezing point of water to determine if it is pure.

Pure water will boil at exactly 100 °C and freeze at exactly 0 °C
The reactivity series of metals

Reactivity serious from most reactive to least reactive
  • Potassium
  • Sodium
  • Lithium
  • Calcium
  • Magnesium
  • Aluminium
  • Zinc
  • Iron
  • Copper
  • Silver
  • Gold

Deducing the reactivity of metals using reaction with water and acid

All of these will react with acid and water

The faster the reaction, the more reactive the metal. We can react each metal with acid and water and then line them up by how vigorously they reacted. This line up can be used to deduce the reactivity of the metals.

Reduction and oxidation

Oxidation is a reaction involving loss of electrons.
Reduction is a reaction involving gain of electrons.


Conditions under which iron rusts

Iron needs water and oxygen to rust.

Iron will rust faster in salty water and acid rain.
How rusting of iron can prevented

Grease, oil, paint and plastic – prevents water or oxygen from coming in contact with the surface of the iron hence not allowing it to rust

Galvanizing – coating iron with a thin layer of zinc which prevents direct contact with water and oxygen hence avoiding rust. It also acts as a sacrificial metal.
How sacrificial protection works for iron

A sacrificial metal more reactive than iron like zinc can be used to coat an iron object (galvanization for zinc). The iron object can avoid rusting because zinc is more reactive than iron and it will go under oxidation first hence slowing down the rusting for iron in case the coating that stops contact with oxygen and water is damaged.

Test for cations and anions

Flame test
Red flame
Flame test
Orange flame
K+ (Potassium)
Flame test
Lilac flame
Ca2+ (Calcium)
Flame test
Brick red flame
NH4+ (Ammonium)
Heating with sodium hydroxide solution
Turns damp red litmus blue, pungent smell
Co32- (Carbonate)
Mixing with acid (hydrochloric acid)
Will produce carbon dioxide gas which will turn lime water cloudy
SO42- (sulfate)
Add a few drops of HCL and barium chloride solution to the test sample
Forms a white precipitate
CL- (chloride)
Add a few drops of nitric acid and then a few drops of silver nitrate solution
White precipitate
Br- (bromide)
Add a few drops of nitric acid and then a few drops of silver nitrate solution
Cream precipitate
I- (iodide)
Add a few drops of nitric acid and then a few drops of silver nitrate solution
Yellow precipitate
Test for gases

Hydrogen – loud pop with burning splint
Oxygen – reignite a glowing splint
Carbon dioxide – bubble through lime water, it turns milky
Ammonia – turns damp red litmus paper blue, pungent smell
Chlorine – turns damp blue litmus paper red, bleaches litmus paper after sometime