Chemical Changes Flashcards

Question

What is an example of a displacement reaction

Answer 1

Iron + copper sulfate --> iron sulfate + copper Fe(s) + CuSO4(aq) -> FeSO4(aq) +Cu(s) Iron loses 2 electrons (2+ oxidised) Copper gains 2 eledteons (-2 reduced) 1) metal ions reduced whereas the metal atom is oxidised

Answer 2

An electric current is passed through an electrolyte (molten/dissolved ionic compound). The ions move towards the electrodes, where they react , the compounds dissolve The positive ions in the electrolyte moves towards the cathode and gains electrons (reduced) The negative ions in the electrolyte moves towards the anode and loses electrodes (oxidised) This creates a flow of charge through the electrolyte as ions travel to electrodes. Ions form an uncharged element and are discharged from the electrolyte

Answer 3

Electrolyte: liquid or solution that conducts electricity Electrode:A solid that conducts electricity when submerged in the electrolyte

Answer 4

1)An ionic solid can't be electrolysed because the ions are in fixed positions 2)Molten ionic compounds can be electrolysed because the ions can move freely and comduct electricity 3)Molten ionic liquids (lead/bromine) are always broken into their elements Positive metal ions reduced to the element as a cathode(lead) Negative non-metal ions oxidised to the element as an anode (bromine)

Answer 5

Electrolysis used when metals more reactive then carbon= this method is expensive Ores contains metals oxides such as aluminium oxide which has a very high melting point so is mixed with cryolite to lower the melting point The molten mixture contaisn free ions- conducts electricity Positive Al3+ ions attracted to the negative electrode where they each pick 3 electrons and turn neutral (aluminium atoms). These then sink at the bottom of the tank. Carbon reacts with oxygen in electrodes as carbon dioixde, carbon lost from the positive electrodes and must be replaced. Negative O2- ions attracted to the posiitve electrode where it each loses two electrons. Neutral oxygen atons combine to form o2 molecules

Answer 6

1) In aqueous solutions there will be hdyrogen ions (H+) a d hydroxide ions (OH-) from the water. 2) At the cathode H+ ions and metal ions are present, hydrogen gas produced if the metal ions form an elemental metal more reactive then hydrogen. If metal ions form elemental metal less reactive then hydrogen a solid layer of pure metal is produced 3) At the anode if OH- ions and halide ions (Cl-, Br-, I-) are present, molecules of halides formed. If no halide ions are present, then the OH- ions are discharged and oxygen willl be formed. 4) This happens in aq solutions as water molecules break down molecules producing hydrogen ions and hydroxide ions that are discharged

Answer 7

1) when you electrolyse an aq solution, the products depend on the reactivity of the ions in the solution compared to H+ and OH- ions 2) At the cathode either a pure metal coating the electrode or bubbles of hydrogen gas produced 3) At the anode bubbles of oxygen gas produced unless halide ions are present 4) choose an electrolyte, pour sample of electeolyte in a large beaker immerse two inert electrodes into the solution and place inverted test tube over each Connect electrodes to a power supply to electrolyse electrodes Continue applying power until no more gas is produced in the test tubes

Answer 8

Chlorine: bleaches damp litmus paper turning it white Oxygen: If you put a glowing splint inside, the oxygen will relight the splint Carbon dixoide: Bubbling carbon dioxide through an aqueous solution of calcium hydroxude causes it to turn cloudy Hydrogen: Hold a lit splint at the open end of the test tube containing hydrogen, squeaky pop.

Answer 9

2H+ + 2e- -----> H2 (negative electrode) 4OH- ---> O2 + 2H2O + 4e- ( ) or (Positive electrode) 4OH- - 4e- ---> O2 + 2H2O. ( )