Chemistry - Cations and Anions

Recall proportions of gases in the air

78% nitrogen

21% oxygen

0.03% - 0.04% carbon dioxide

about 1% argon.(Trace gas)

H20 vapour (Trace gas)

Describe how to test for hydrogen

The squeaky pop test-

put a lit splint into the gas sample if present there will be a squeaky pop

Describe how to test for oxygen

Glowing splint-

If you put a glowing splint in a test tube and it relights, oxygen is present

Describe how to test for carbon dioxide

Bubbling the gas through the liquid-

If you bubble the gas through the limewater and it turns cloudy/milky, carbon dioxide is present

Describe how to test for chlorine gases

The test for chlorine gas-

use damp blue litmus paper. The blue colour will turn to red and then to white. Chlorine gas reacts with water to produce an acidic solution which is also an effective bleach.

Describe the use of hydrogen

Hydrogen can be used to power vehicles, generate electricity, power industry and heat our homes and businesses.

Describe the use of oxygen

Oxygen is used in power plants to enhance the efficiency of fuel combustion, reducing emissions and improving energy output.. Oxygen is used in aerobic respiration to release energy to the body.

Describe the use of Carbon dioxide

CO2 is also widely used in food and beverage production, the creation of metal, cooling, fire suppression and in greenhouses to stimulate plant growth.

Describe the use of Chlorine gases

Used in water disinfection, bleach production, and manufacturing PVC.

How to experimentally prepare oxygen

Place manganese(IV) oxide in a conical flask, collect 50 cm³ of hydrogen peroxide, set up the apparatus, pour the hydrogen peroxide into the thistle funnel, wait 5 seconds, collect the gas in inverted water-filled test tubes until you have two tubes of gas, then remove the test tubes for further tests.

Balanced symbol equation for preparation of oxygen

2H2O2→ 2H2O + O2

How to experimentally prepare hydrogen

Place zinc in a conical flask, collect 50 cm³ of hydrochloric acid, set up the apparatus, pour the acid into the thistle funnel, wait 5 seconds, collect the gas in inverted water-filled gas jars/test tubes until you have three jars/tubes of gas, then remove them for further tests.

Balanced symbol equation for prep of hydrogen

Zn+2HCl→ZnCl2+H2

How to experimentally prepare carbon dioxide

Place calcium carbonate in a conical flask, collect 50 cm³ of hydrochloric acid, set up the apparatus, pour the acid into the thistle funnel, wait 5 seconds, collect the gas in inverted water-filled gas jars/test tubes until you have three jars/tubes of gas, then remove them for further tests.

Balanced symbol equation for the prep of carbon dioxide

CaCO3+2HCl→CaCl2+CO2+H2O

What is thermal decomposition

Thermal decomposition is a chemical reaction where a single compound breaks down into two or more simpler substances when heated. This process often requires high temperatures to provide the necessary energy to break the chemical bonds.

Examples of Thermal decomposition

When heated, calcium carbonate decomposes into calcium oxide (quicklime) and carbon dioxide gas.

CaCO3→CaO+CO2

When heated, lead(II) nitrate decomposes into lead(II) oxide, nitrogen dioxide, and oxygen gas.

2Pb(NO3)2→2PbO+4NO2+O2

What are cations

Cations: Positively charged ions that are formed when an atom loses one or more electrons. (e.g., Na⁺, Ca²⁺)

What are anions

Anions: Negatively charged ions that are formed when an atom gains one or more electrons. (e.g., Cl⁻, SO₄²⁻)

Explain how to perform a flame test

dip a clean wire loop into a solid sample of the compound being tested.

put the loop into the edge of the blue flame from a Bunsen burner.

observe and record the flame colour produced.

What happens in a precipitation reaction

A precipitation reaction occurs when two soluble salts in aqueous solutions are mixed, resulting in the formation of an insoluble solid called a precipitate. This happens due to the reaction between the ions of the salts, which form a compound that does not dissolve in water.

An example of a precipitation reaction

LiCl (s)→Li+(g)+Cl−(g)