Oxygen & Oxides

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Preparation of oxygen experiment and its method

Method: 2 to 3 spatula measure of Manganese (IV) oxide into CONICAL FLASK.

Assemble the apparatus: Includes Conical flask, thistle funnel, gas jar, water (tub?), delivery tube

Pour 20cm3 of hydrogen peroxide solution into thistle funnel.

Allow bubbles of gas to escape from delivery tube (15-30 seconds) then collect five test tubes of oxygen by displacement of water.

Experiment: HYDROGEN PEROXIDE SLOWLY DECOMPOSES TO FORM OXYGEN GAS AND WATER. THIS EXPERIMENT IS USED TO OBTAIN OXYGEN IN A LAB. A CATALYST ( manganes (IV) oxide) SPEEDS UP THE PROCESS.

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Properties of Oxygen

Colourless

No Smell/ odourless

not very soluble in water

not flammable

similar density compared to air

METAL OXIDES DISSOLVE TO FORM ALKALINE

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Reaction with Oxygen (Mg)

Oxidation reaction - When an element reacts with Oxygen.

Magnesium + Oxygen -- Magnesium Oxide

Balanced Equation :

2Mg(s) + O2(g) -- 2Mg(s)

Magnesium burns oxygen with a white bright LIGHT.

Magnesium is a white powder which forms alkaline solution if distilled water is added to it.

If SOLUBLE ALL metal oxides dissolve in water to form alkaline solutions with a Ph GREATER than 7.

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Reaction with Oxygen (Sulfur)

Forms COLOURLESS sulfur dioxide gas.

Burns with a blue flame

sulfur + Oxygen ----Sulfur dioxide

S(s) + O2 (g) ----- SO2 (g)

Is ACIDIC when it dissolves in distilled water.

This is because sulfur is a NON metal and ALL non metal oxides are acidic. If they dissolve in water they form solutions with a Ph LESS than 7.

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Reaction with Oxygen (Carbon)

Burns in air to form colourless carbon dioxide gas.

Carbon + Oxygen ---- Carbon dioxide

Balanced Equation:

2C(s) + O2 (g) --- CO2 (g)

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Lab Prep of Carbon Dioxide

CO2 is prepared in a lab by reacting hydrochloric acid with a metal carbonate (usually calcium carbonate)

Equations

Calcium carbonate + Hydrocloric Acid ---Carbon dioxide + Water + Calcium chloride

CaCO3(s) + 2HCL(aq) ---- CO2(g) + H2O (l) + CaCl2 (aq)

For diagram look at page 43 of revision guide

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Thermally Decomposing a Metal Carbonate

Thermal decomposition means the metal carbonate will break down when heated .

We can test for the presence of CO2 by bubbling through a straw into limewater.

Examples of thermal decompostion are:

zince carbonate ---- zinc oxide + Calcium carbonate

ZnCO3(s) ---- ZnO (s) + CO2(g)

Iron (III) carbonate ----- Iron (II) oxide + carbon dioxide

FeCO3(s) ---- FeO(s) + CO2 (g)

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Uses of Carbon Dioxide

Used in fire extinguishers because it is more dense than air therefore it covers the fire and stops oxygen getting to it. Carbon dioxide doesnt burn so the fire goes out.

It is also used to make fizzy/carbonated drinks. Is only slightly soluble in water but is added to drinks under pressure which INCREASES its solubility (so when the cans are opened the pressure is released and the drink fizzes)

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Climate Change

Greenhouse gases stop heat energy leaving the earths atmosphere which keeps the planet warmer than it would/should be.

Scientists believe levels of carbon dioxide are increasing due to excessive burning of fossil fuels and deforestation ( cutting down trees so less photosynthesis is happening to remove carbon dioxide from the atmosphere) .

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