S4 - Inorganic Chemistry Flashcards
similarities in the reactions of alkali metals with water:
-they have characteristic properties due to the single electron in their outer shell
-all of the metals in group one react vigorously with water to create an alkaline solution and hydrogen
differences between the reactions of the alkali metals with a air and water creating a trend in reactivity:
-they all react with oxygen to create an oxide
-more bubbles with reaction with water = more vigorous reaction = more reactive alkali metal
-reactivity increases down the group-therefore reactivity increase from lithium -> sodium -> potassium
metal, reaction with water:
-lithium, frizzes steadily (less)
-sodium, melts into a ball then fizzes quickly
-potassium, gives off sparks and hydrogen burns with a lilac flame (most)
how to predict the properties of other alkali metals in Group 1?
-increase in reactivity down the group applies for any reaction in group 1
halogens (group 7): colours + physical states (at room temperature) and trends in physical properties of these elements
-chlorine is a yellow-green gas
-bromine is a red-brown liquid
-iodine is a purple solid
-there is a trend in state from gas -> liquid -> down the group
how to predict the properties of halogens in Group 7?
-there is a trend in state from gas -> liquid -> solid down the group
-this is because the melting and boiling increase as you go down the group
-from this, you can predict that any halogens above chlorine will be gases (their boiling points will be even lower), and any below iodine will be solids (their melting points will be even greater) chlorine (less) -> bromine -> iodine (most)
displacement reactions involving halogens and hallides:
-a more reactive halogen can displace a less reactive in an aqueous solution of its salt
-e.g: chlorine will displace bromine if you bubble the gas through a solution of potassium bromide:
chlorine (less) + potassium bromide -> potassium chloride + bromine (more)
-chlorine will displace bromine and iodine
-bromine will displace iodine but not chlorine
-iodine can replace neither chlorine or iodine
-this happens because as you go down the group, the reactivity of halogens decreases
aproximate percentages by volume of the four most abundant gases in dry air:
-nitrogen: 78%
-oxygen: 21%
-argon: 0.9%
-carbon dioxide: 0.037%
how to determine the percentage by volume of oxygen in air using experiments involving the reactions of metals (e.g: iron) and non-metals (e.g: phosphorus) with air:
example using copper:
-100 cm^3 of air passed from side to side over copper that was being heated with a bunsen burner
-all oxguen in air will react with copper
-it’s a closed system-therefore, no air could get in or out
-as it passed, the volume stops decreasing, then record the volume of remaining air
-there would be about 79cm^3 left, showing that 21cm^3 of the original 100 cm^3 of air was oxygen
-the reaction happening in this case (with copper) is:
copper + oxygen -> copper(II) oxide//2Cu(s) + O2 (g) -> CuO(s), would notice black copper oxide forming
combustion of elements in oxygen, including magnesium, hydrogen and sulfur:
combustion is an example of oxidation:
-in an oxidation reaction, a substance gains oxygen
-metal and non-metals can take part in these reactions
-e.g: magnesium+oxygen-> magnesium oxide
2Mg+02-> 2MgO
-e.g: sulfur+oxygen-> sulfur dioxide
S+O2->SO2
-e.g: hydrogen+oxygen->water
2H2+O2->2H2O
the formation of carbon dioxide from thermal decomposition of metal carbonates, including copper(II) carbonate:
-metal carbonate -(heat)-> metal oxide + carbon dioxide
-e.g: copper(II) carbonate -(heat)-> copper(II) oxide + carbon dioxide or CuCO3->CuO+CO2
greenhouses gases contributing to climate change: carbon dioxide
-greenhouse gas effect mantains temperatures on Earth high enough to support life
-greenhouses gases include: water vapor, CO2, CH4
explanation of the greenhouse gas effect:
-electromagnetic radiation at most wavelengths fom the sun passes through the Earth’s atmosphere
-the Earth absorbs some radiation and thus warms up (essential for life on Earth). But some is radiated from the Earth as infrared radiation
-some of this IR radiation is absorbed by greenhouse gases in the atmosphere
-atmosphere warms up leading to the greenhouse effect and global warming
-global warming is an ‘enhaced greenhouse effect’
-an increase in average global temperature is a major cause of climate change
practical: determine the approximate percentage by volume of oxygen in air using a metal or non-metal: iron
-you can use iron to determine the percentage of oxygen in the air because iron reacts with oxygen in the air to form rust, so iron will remove oxygen from the air
1) first soak some iron wool in acetic acid, then push the wool into a measuring cylinder and invert the measuring cylinder into a beaker of water
2) records the starting position of the water using the scale on the measuring cylinder-this is the starting volume air
3) over time, the level of the water in the measuring cylinder will rise
4) this is because the iron reacts with the oxygen in the air to make iron oxide. The water rises to fill the space the oxygen took up
5) leave the measuring cylinder for around a week or until the water level stops changing
6) record the finishing position of water-this is the final volume of air-
-to calculate the percentage of oxygen just put the volumes you recorded into this formula:
start volume-final volume/start volume x 100
-the answer you should get is about 20%
