Oxygen Flashcards
How do we determine the % of oxygen in the air?
This technique involves passing a known volume of air over a heated metal which reacts with and therefore removes the oxygen from the air. Two gas syringes are connected together with a delivery tube. In the tube is some freshly cut copper metal. In one gas syringe there is 100cm3 of air; the other is empty.
What is the method to find he % of oxygen in the air?
- Set up the apparatus so that there is 100 cm3 of air in one gas syringeand none in the other.
- Heat the copper metal strongly using the blue Bunsen flame and pass the air in the syringe slowly back and forth over the heated metal.
- Note the volume of air each time you pass the air over the metal and continue until the volume no longer decreases.
- Leave the apparatus to cool for a few minutes and read of the final volume of gas left in the syringe.
What is the formula for finding the % of oxygen in the air?
Volume at start- vol at the end/ total vol= % of oxygen in the air
How does copper change its appearance during the experiment? (finding the % of oxygen in the air)
it turns from pinkish-red to black
what is the word equation for the reaction of copper and oxygen?
copper + oxygen → copper (ll) oxide
Is the reaction of copper and oxygen a physical or chemical change?
it’s a chemical change (synthesis) as a new chemical is formed
How does the copper change in mass when it reacts with oxygen?
it increases in mass
Give a use for these gases:
-Carbon dioxide
-iron
-fire extinguishers
-to fill light bulbs
What apparatus are used for the rusting of iron in a gas jar?
-gas jar
-water bowl
-iron
-water
-scale
What is the method of the rusting of iron in a gas jar?
-Set up the apparatus (test tube with iron wool inside a beaker filled with water)
Mark the water level on the scale
-leave until the iron rusts
-mark the new water level on the scale
What happens when the iron rusts?
it reacts with the oxygen and water vapour from air. as the oxygen is used a vacuum is created. the water level inside the gas jar rises upwards and takes the place of the used up oxygen
How does the iron change when it rusts?
it changes from a shiny grey metal to a dull red/brown colour
How do we calculate the % of oxygen in the air using the rusting of iron in a gas jar method?
the marks on the scale at the start and the end of the experiment show how much oxygen was used up and can be used to calculate the %of oxygen in the air
What is the method of the burning of a candle in a gas jar?
- Mark a scale on the gas jar.
- 1⁄2 fill the water bowl with water.
- Place the candle in a crucible on the water.
- Light the candle.
- Gently place the inverted gas jar over the candle.
- Mark the starting water level.
- When the candle goes out mark the new water level on the scale.
What are the results of burning a candle in a gas jar?
The candle will burn until the supply of oxygen runs out. As the oxygen is used
up burning the candle, the water level inside the gas jar will rise upwards.
How do we calculate the % of oxygen in the air by burning a candle in a gas jar?
The rise in the water level can be used to calculate the % of Oxygen in air.
What is the formula to calculate the % of oxygen in the air?
% oxygen= finish level - start level/total on scale x 100
(/ is divide)
What is the chemical name for rust?
hydrated iron (lll) oxide
What are two gases that could form when a candle burns?
carbon dioxide and hydrogen oxide (water)
What does Hydrogen peroxide dissolved in water make?
it makes a colourless solution
What does hydrogen peroxide slowly decompose to make?
water and the colourless gas oxygen
What is the word equation for the decomposition of hydrogen peroxide?
Hydrogen peroxide → water + oxygen
How can the reaction (decomposition of hydrogen peroxide) be made faster?
By adding the black solid compound manganese (lV) oxide
Why does manganese (lV) oxide make the reaction faster?
because it acts like a catalyst
What is a catalyst?
something that speeds up chemical reactions without being used up
What is the method for the preparation of oxygen?
- The apparatus is set up as in the diagram with some hydrogen peroxide
in the flask. - A spatula full of manganese (IV) oxide is added to the hydrogen
peroxide. - The gas is collected over water.
- After collecting the gas hold a glowing splint in it and note down the
result.
What colour is oxygen?
it’s colourless
What is the symbol for oxygen?
O
What is the formula of oxygen gas?
O2
Oxygen gas exists as diatomic molecules. What does this mean?
Two atoms chemically bonded together in one molecule
Which gas forms the major part of the air?
nitrogen
The gas nitrogen is inert. What does this mean?
it doesn’t react with other chemicals
What is the apparatus used in the experiment to show that manganese (lV) oxide catalysis the decomposition of hydrogen peroxide?
Filter paper, test-tube with manganese (IV) oxide, filter funnel, 250cm3 beaker, 250cm3 conical flask, measuring cylinder, hydrogen peroxide solution, crystallising dish.
What is the method of the experiment to show that manganese (lV) oxide catalysis the decomposition of hydrogen peroxide?
- Measure 25cm3 of hydrogen peroxide solution and pour it into thebeaker.
- Put the manganese (IV) oxide onto the filter paper.
3 Now weigh the filter paper and the manganese (IV) oxide
together. Record the mass in the results table. - Add the manganese (IV) oxide to the hydrogen peroxide solution. Do not spill any manganese (IV) oxide.
KEEP YOUR FILTER PAPER. - When the bubbling in the beaker has stopped filter the contents of
the beaker through the FILTER PAPER YOU USED AT THE START. You must make sure all the manganese (IV) oxide is washed out of the beaker and into the filter paper. - Leave the filter paper containing the manganese (IV) oxide in the filter funnel for about 10-15 minutes to dry a little. Write your name on a label and stick it on a crystallising dish.
- Remove the filter paper and manganese (IV) oxide and put it in your crystallising dish. Put it in the fume cupboard until next week.
- Remove the filter paper (NEXT WEEK) from the crystallising dish
and weigh it. THE MASSES SHOULD BE THE SAME.
What is the initial mass of manganese (lV) oxide and filter paper?
2.94g
What is the final mass of manganese (lV) oxide and filter paper?
2.94g
What is the initial appearance of manganese (lV) oxide?
Black solid
What is the final appearance of manganese (lV) oxide?
black solid
Which chemical releases oxygen?
hydrogen peroxide
what is the black solid used in the experiment?
Manganese dioxide/manganese (IV) oxide
Name the gas made in the experiment. How would you test for this gas?
Oxygen. Insert a glowing splint into the gas. The splint will relight.
After filtering what was left in the conical flask?
water
What happens when metals react with oxygen?
they form metal oxides, and many metals burst into flames when they react with oxygen, with a variety of coloured flames. Metal oxides are also solids
How are the reactions of metals and oxygen carried out?
The reactions are carried out in a gas jar full of oxygen (not air). The metal is placed on a deflagrating spoon, heated and then placed into the gas jar.
What happens when non-metals react with oxygen?
they form nonmetal oxides. Many non-metals burst into flames when they react with oxygen, with a variety of
coloured flames. Non-metal oxides are usually gases.
What is an example of a metal reacting with oxygen?
burning magnesium
What is an example of a non-metal reacting with oxygen?
burning sulphur
Which element forms an oxide that produces the most acidic solution?
sulphur
Which oxides are gaseous?
carbon dioxide and sulphur dioxide
What colour are the oxides of lithium and magnesium?
white
What are the word equations for the formation of the four oxides?
lithium + oxygen → lithium oxide
magnesium + oxygen → magnesium oxide
carbon + oxygen → carbon dioxide
sulfur + oxygen → sulfur dioxide
What are the chemical formulae of the four oxides?
Lithium oxide = Li2O
Magnesium oxide = MgO
Carbon dioxide = CO2
Sulfur dioxide = SO2
What common name do we give to the main oxide of
hydrogen?
water
What is the pH of hydrogen’s oxide?
pH7
