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chemistry topic 1: key concepts in chemistry. bonding: ionic bond is between a metal and a non-metal. covalent bonding is between 2 non-metals. metallic bonding is between 2 metals. all calculations: moles=mass over RFM. concentration =mass over volume. molar gas volume=volume over 24. percentage yield=actual over theoretical times by 100. empirical formula: step1 - find moles of each element . step2- divide each molar value by smallest mole value. step3 - write the formula as ratio where the answer to step 2 is a small number in a chemical formula. topic 2: states of matter. filtration core practical: 1) pour solution into evaporating dish and gently heat 2) once crystals start to form, remove from heat to cool 3) leave on windowsill for a week to allow crystals to increase in size 4) dry with paper towel topic 3: chemical changes. solubility rules: all nitrates are soluble. all chlorides except silver an lead are soluble. all sulphates are soluble except for lead, barium and chloride. carbonates/hydroxides are insoluble except sodium, potassium and ammonium. precipitation reaction (insoluble salt) practical: 1) Place a known volume of one soluble salt solution in a beaker . 2) Keep adding the other soluble salt solution and stir to mix until no more precipitate forms. 3) Filter out the precipitate. 4) The residue is the insoluble salt you are trying to get. 5) Wash residue with water. 6) Dry the insoluble salt crystals. soluble salt practical: 1) gently warm acid 2) add excess base (copper oxide in most cases) 3) filter off excess base 4) evaporate any water molten electrolysis practical: 1) Positive ions move to the cathode (the negative electrode). When they get there, they pick up electrons from the electrode to form neutral atoms. 2) Negative ions are attracted to the positive anode, and are discharged by losing electrons. aqueous electrolysis practical: 1) Two ions are attracted to the cathode. The hydrogen ion and the metal ion are attracted to the cathode. 2) Two ions are attracted to the anode. The hydroxide ions and halide ions are attracted to the anode. 3) Metal reactivity is compared to hydrogen. If the metal element formed during electrolysis is more reactive than hydrogen, then hydrogen will be produced at the cathode. If the metal element formed is less reactive than hydrogen, then the metal is produced at the cathode. electrolysis of copper sulphate: 1) Pour some copper sulfate solution into a beaker. 2) Place two graphite rods into the copper sulfate solution. Attach one electrode to the negative terminal of a dc supply, and the other electrode to the positive terminal. 3) Completely fill two small test tubes with copper sulfate solution and position a test tube over each electrode as shown in the diagram. 4) Test any gas produced with a glowing splint and a burning splint. topic 4: extracting metals and equilibria. reactivity series. most to least reactive: potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, hydrogen, copper, silver, gold equilibrium: as reactants A & B react, their concentration will fall so the forward reaction slows down. but as more of the products are formed, their concentration rise and the backward reaction speeds up. after a while, the forward and backward reactions will go at the same rate and they will be at equilibrium. dynamic equilibrium is where the forward and backwards reactions have equal rate at the same time so the concentration of reactants and products won't change. sometimes equilibrium can have more reactants than products or vice versa. the position of equilibrium depends on the conditions of: temperature for energy, pressure for rate of reactions and concentration of reactants/products. if temperature is low, equilibrium moves to exothermic and produce more heat and if it's high equilibrium moves to endothermic to cool down. if pressure is high, equilibrium moves to fewer moles to increase pressure and if pressure is low, equilibrium moves to greater moles to decrease pressure. if reactant concentration is high, equilibrium uses up more reactants and if product concentration is high, equilibrium uses up more products. topic 7: rates of reactions. rate of reaction = product formed over time disappearing cross: 1) Using a measuring cylinder, add 50 cm3 of dilute sodium thiosulfate solution to a conical flask. 2) Place the conical flask on a piece of paper with a black cross drawn on it. 3) Using a different measuring cylinder, add 10 cm3 of dilute hydrochloric acid to the conical flask. Immediately swirl the flask to mix its contents, and start a stop clock. 4) Look down through the reaction mixture. When the cross can no longer be seen, record the time on the stop clock. 5) Repeat steps 1 to 4 with different starting temperatures of sodium thiosulfate solution. volume of gas (with gas syringe): 1) mix reactant with acid 2) measure time for gas syringe to fill up 3) once gas syringe has stopped moving, stop timer and record the time.