Chemistry GCSE- C3

Question	Answer
What is shielding? What are the consequences?	Shielding is when their is a lot of electrons on the inner rings of an atom, thus "blocking" the pull of the atoms "pull". This means that it is easier for an atom to lose an electron, but it is also harder to gain an electron.
What reacts vigorously with water?	Lithium, sodium and Potassium
Hydrogen test (squeaky pop test)	You light a splint, you put it near the liquid, if it "pops", hydrogen is present.
Alkali Metals (group 1)	As you go down group 1, the alkali metals become MORE REACTIVE and have LOWER MELTING AND BOILING POINTS
Alkali Metals continued	Keen to lose their one outer electron to form a 1+ Ion. This means that covalent bonding is out of the question. They produce white compounds that dissolve in water to form colourless solutions.
Halogens	The halogens(group 7) are all Non-Metals with COLOURED VAPOURS. They all exist as molecules which are pairs of atoms.
What do halogens form?	The halogens form 1- ions called ionic bond with metals. They form 1- ions called halides when they bond with metals.
Transition Elements	They are typical metals. They often have more than one ion. The different ions usually form different-coloured compounds. They are colourful due to the transition metal ion. Transition metal and their compounds all make good catalysts, such as Iron for the Haber process.
Hardness of water. What causes hard water?	With soft water, you get a nice lather with soap. But with hard water you get scum. Hard water is caused by dissolved calcium ions and magnesium ions in the water reacting with the soap to make scum that is insoluble. So to get a decent lather, you need to use more soap.
What ions cause hard water?	Hardness in water is caused by Ca2+ and Mg2+ ions. Rain falling on some types of rocks can dissolve compounds like magnesium sulphate and calcium sulphate.
Why isn't hard water all that bad?	Ca2+ ions are good for healthy teeth and bones. Studies show that people who live in hard water areas are at less risk of heart disease.
How can you make hard water soft?	You can make hard water soft by removing the dissolved Ca2+ and Mg2+ ions.
Temporary and Permanent hardness?	Temporary hardness is caused the hydrogencarbonate ion HCO-3, in Ca(HCO3)2 Permanent hardness is caused by dissolved calcium sulphate.
How can you remove temporary hardness?	T-Hardness is removed by boiling. When heated, the hydrogen carbonate decomposes to form calcium carbonate which is insoluble. This solid is the lime scale.
How can you remove both types of hardness?	Both types of hardness can be softened by adding washing soda(sodium carbonate) to it. The added carbonate ions react with the Ca2+ and Mg2+ ions to make an insoluble precipitate of calcium carbonate and magnesium carbonate. The Ca2+ and Mg2+ ions are no longer dissolved in the water so they cant make it harder
How else can it be removed?	Both types of hardness can also be removed by running water through 'ion exchange columns'. The columns have lots of sodium ions(or hydrogen ions) and 'exchange' them for calcium or magnesium ions in the water that runs through them.
Reversible Reactions	Reversible reactions will reach equilibrium. Equilibrium means that the amounts of reactants and products will reach a balance. Overall effect is nil.
Temperature's effect on reactions.	If you raise the temperature, the endothermic reaction will increase to use up extra heat. If you lower the temperature, the exothermic reaction will increase to give out more heat.
Pressure's effect of reactions	Raise pressure=Less volume Lower Pressure=More Volume
Haber process	Nitrogen and Hydrogen are needed to make Ammonia. Nitrogen is obtained easily from the air, which is 78% nitrogen. Hydrogen comes from natural gas or from other sources like crude oil. Some of the nitrogen and hydrogen reacts to form ammonia. The reaction happens in both directions.
Haber Process conditions	Pressure= 200 Atmospheres Temperature=450'c Catalyst=Iron
Haber Process continued	Higher Pressures favour the forward reaction, which results in a higher percentage yield. The forward reaction is exothermic, so yield of ammonia is greater at lower temperatures. However, lower temperatures mean a lower rate of reaction. Ammonia is formed as a gas but as it cools in the condenser it liquefies and is removed.
Haber Process efficiency	Unused hydrogen and nitrogen are recycled so nothing is wasted.
Haber process catalyst	The iron catalyst makes the reaction go faster, which gets it to the equilibrium proportions more quickly, however doesn't affect the position of equilibrium.
Alcohols	Alcohols have an '-OH' Functional group and end in '-ol'
Alcohol properties	Alcohols are flammable. They burn in air to produce CO2 and H2O. The first three alcohols all dissolve completely in water to from neutral solutions. They react with sodium to give hydrogen and alkoxides.
Alcohol solvents	Alcohol can be used as solvents as they can dissolve most compounds that water dissolve.
Carboxylic Acids	Names end in '-anoic' acid.('meth/eth/prop)
Carboxylic Acids in Industry	C-Acids with longer chains of carbon atoms are used to make soaps and detergents.
Test for positive ions	Lithium(Li+),=Crimson Flame Sodium(Na+)=Yellow flame Potassium(K+)=Gives a lilac flame Calcium(Ca2+)=Red Flame Barium(Ba2+)=Green flame
Test for Metal Ions	Add sodium hydroxide Calcium=White Precipitate Copper=Blue precipitate Iron(II)=Green precipitate Iron(III)=Brown Magnesium=White Aluminium= White at first
Test for Negative Ions- Testing for carbonates	Bubble through limewater, if cloudy, carbon dioxide is present. This test works for carbonate ions.
Test for halide ions	Add dilute nitric acid, followed by silver nitrate solution. Chloride gives a white precipitate of silver chloride. Bromide gives of a cream precipitate of silver bromide. Iodine gives a yellow precipitate of silver iodine
Sulphate ions	To test for a sulphate ion, add dilute HCL, flowed by barium chloride solution. A white precipitate of barium sulphate means the original compound was a sulphate.

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