Section 2: Chemistry of the Elements Flashcards
Metal oxides are basic. What does this mean?
they will neutralise acids
Metal oxides which dissolve in water form solutions with a pH of…
more than 7
Non-metal oxides will dissolve in water to form solutions with a pH of…
less than 7
Give a property of the noble gases
they are inert
group one elements are called…
the alkali metals
Why are group 1 named the alkali metals?
They react vigorously with water, producing a metal hydroxide solution (alkaline)
Name 1 observation you could make when lithium reacts with water
fizzing/effervescence, as the lump of lithium moves slowly around the surface until it disappears.
AS you go down group 1 what happens to the reactivity of the elements?
it increases
When alkali metals react with water, what is the gas produced? (fizzing)
hydrogen H2
Which is moe reactive, potassium of lithium?
potassium
Why do atoms lose electrons more easily as you go down group 1?
Because as you go down the group, the no. of shells (&period) increases. Thus, the outermost electron becomes further from the nucleus, causing a lesser attraction between the two.
What is the name given to elements in group 7?
the Halogens
As the atomic no. of the halogens increases, what changes can be seen in relation to colour and boiling point?
as you go down the group, the colour darkens and the boiling point increases (thus they go from solids to gases)
Are elements higher up group 7 more or less reactive than those lower down? WHY??
more reactive, because the shell missing an electron is nearer to the nucleus, thus the pull from the positive nucleus is greater.
Which ions are formed when Hydrogen Chloride is dissolved in water? What is the name of this process?
H+ ions and Cl-
Dissociation
When Hydogen Chloride dissolves in water, the solution formed is called…
Hydrochloric acid
Why is this solution acidic?
Because it contains H+ ions
However, what will happen if Hydrogen Chloride is dissolved in an organic solvent, e.g methylbenzene?
It doesn’t dissociate into H+ and Cl- ions, therefor it isn’t acidic
Define a displacement reaction
When a more reactive element displaces a less reactive element from a compound
If you add chlorine water to potassium iodide, the solution will react to form… (displacement reaction)
potassium chloride (+ iodine)
A loss of electrons (or a gain of oxygen) is called…
oxidation
A gain of electrons is called…
reduction
What does an oxidising agent do?
accepts electrons and becomes reduced
What does a reducing agent do?
Donates electrons and gets oxidised
Reactions where reduction and oxidation occur simultaneously are called…
Redox reactions
Acid+ Metal —>
Salt + Hydrogen
When different metals are reacted with dilute acids, how can you use this reaction to determine the reactivity of the metal?
the more reactive the metal, the faster the reaction will occur. The speed of the reaction is indicated by the rate at which the bubbles of hydrogen are given off (metal+acid–>salt+hydrogen)
What sort of salts will hydrochloric acid produce?
chloride salts
What sort of salts will sulfuric acid produce?
sulfate salts
(very reactive)Metal + Water –>
Metal Hydroxide + Hydrogen
(less reactive)Metal + Steam –>
Metal oxide +Hydrogen
Magnesium + Steam –>
Magnesium oxide + Hydrogen
Calcium + Water –>
Calcium Hydroxide + Hydrogen
What two variables does iron need to be in contact with in order to rust?
oxygen from the air, and water
iron + oxygen + water –>
hydrated iron(111) oxide (rust)
Which barrier methods are used to prevent iron from rusting and when?
Painting/coating with plastic: for big/small structures alike… can be decorative
Oiling/Greasing: used when moving parts are involved (e.g on bike chains)
Describe the process of the sacrificial protection of iron using Zinc as a sacrificial metal?
Zinc is more reactive than iron, being further up the reactivity series. A coating of zinc is sprayed onto the object- this is known a galvanising (alternatively big blocks of zinc can be bolted to the iron- for ships/underground pipes). The zinc will be oxidised instead of the iron.
Describe the composition of the Atmosphere? (percentages of each gas)
78% Nitrogen, 21% Oxygen, (1% Argon, 0.4%CO2) also water vapour
Describe how to investigate the proportion of oxygen in the atmosphere using copper
When heated, copper reacts with oxygen to make copper oxide- thus using up oxygen.
If you heat an excess of copper in a sealed tube and pass air over it using two sealed syringes, you can use the markers on the syringes to tell how much oxygen has been used up. If you start with around 100cm3 of air, you’ll end up with around 80cm3 when the reaction’s finished. This shows that, if 20cm3 of air has gone around 20% of the air must be oxygen.
Describe how to investigate the proportion of oxygen in the atmosphere using iron (white phosphorous can also be used in the same way- it smoulders in air to produce phosphorus oxide)
Iron reacts with oxygen to form rust- it removes oxygen from the air.
- Soak some iron wool in acetic acid (catalyst). Then push the wool into a test tube. Put your thumb on the end and invert the tube into a beaker of water.
- Over time, the water level in the test tube will rise, because the iron reacts with the oxygen in the air so the water rises to fill the space the oxygen took up.
- To find the %air that is oxygen you need to mark the starting and finishing position of the water.
- Fill the tube up to each mark with water and pour the contents into a measuring cylinder to find out the volume of air at the start and end.
- use the difference between the start and end volumes to work out the %of the starting volume that has been used up- it should be about 20%
What are the two methods for collecting oxygen gas?
- COLLECTION OVER WATER: you can use a delivery tube to bubble the gas into an upside-down measuring cylinder or gas jar filled with water
- GAS SYRINGE
How can you make oxygen in the lab? (equation & catalyst)
hydrogen peroxide decomposes to water and oxygen withh the catalyst manganese(lV) oxide. 2H202 –> 2H2O + O2
Describe the observations you could make when magnesium burns in air (oxygen)
bright white flame, white powder (magnesium oxide) formed.
Describe the observations you could make when Carbon burns in air (oxygen)?
orangey/yellowy flame, produces carbon dioxide gas
Describe the observations you could make when sulfur burns in air (oxygen)
pale blue flame, produces sulfur dioxide
sulfur dioxide, when dissolved in water, is…
ACIDIC
carbon dioxide hen dissolved in water is…
slightly acidic
when magnesium oxide is dissolved in water it is…
slightly alkaline
When should upward delivery in a test tube be used to collect a gas?
if the gas is lighter/less dense than air- e.g H2
When should downward delivery be used to collect a gas?
when the gas is denser than air e.g CO2, Cl2
hydrochloric acid + calcium carbonate –>
2HCl + CaCO3 –>
calcium chloride + water + carbon dioxide
CaCl2 + H2O + CO2
copper carbonate thermally decomposes to form…
carbon dioxide and copper(ll) oxide
what property of carbon dioxide makes it ideal to be used in the production of fizzy/carbonated drinks?
it is soluble in water
what property of carbon dioxide makes it ideal to be used as a fire extinguisher?
it is denser than air, so will smother the flames, stopping the oxygen that the fire needs from reaching it
two examples of human activity that affect the amount of carbon dioxide in the atmosphere?
- deforestation: fewer trees mean less CO2 is removed from the atmosphere via photosynthesis
- burning fossil fuels- releases CO2 in these fuels into the atmosphere
name three greenhouse gases
methane, carbon dioxide, water vapour
What do greenhouse gases do?
act as an insulating layer, causing heat radiation from the sun to become trapped in the earth’s atmosphere
what happens to the reactivity of the alkali metals as you go down group 1 and why?
they get more reactive because they lose electrons more easily as the shells increase meaning the attraction between the outermost electron and the nucleus becomes less
what are two ways ethanol can be made?
ethane and steam, or fermentation
what temperature does the reaction of ethene and steam to make ethanol need?
300 degrees C
what pressure does the reaction of ethene and steam to make ethanol need?
60-70 atm
what is the catalyst used for the reaction between ethene and steam to make ethanol?
phosphoric acid
what is symbol equation for the reaction between ethene and steam?
C2H4 + H2O –> C2H5OH
what is the raw material needed for fermentation to occur?
sugar eg glucose
how is sugar converted to ethanol in fermentation?
using yeast
what temperature does the process of fermentation need?
30 degrees C
how fast is the reaction between ethene and steam to make ethanol compared to fermentation?
much faster
what are three disadvantages to the method of using fermentation to produce ethanol?
very slow, very impure so needs to be distilled, high labour costs
what is the overall cost of fermentation like compared to the cost of ethene and steam in the production of ethanol?
lower temp, so cheaper equipment is needed, but the labour costs are higher
what is a disadvantage of using ethene + steam to make ethanol as opposed to fermentation?
crude oil is needed to make the ethanol, and crude oil is a finite resource, so one day will become very expensive
how can you turn ethanol back into ethene?
by dehydrating it
how is ethanol vapour dehydrated?
it is passed over a hot catalyst of aluminium oxide
