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21 Cards in this Set
- Front
- Back
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What is the formula for rust?
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Fe2O3XH2O
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What are the three special properties of d block transition metals?
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1. They can have varying oxidation states
2. They can have different colours in compounds 3. They can act as effective catalysts |
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Why are there different colours formed by these metals?
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Because when an electron moves from a higher energy level (4s) to a lower energy level (3d) a photon of light is released.
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Why do these metals make good catalysts?
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The outer electrons in the 3d and 4s orbitals form weak bonds with the reactants, once the products are formed these bonds break.
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What does the color of a transition metal compound depend on?
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1. The number of electrons in the outer orbitals
2. The arrangement of ligands around the metal ion. 3. The type of ligand |
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What is a ligand?
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A NEGATIVELY CHARGED molecule or ion that has a lone pair of electrons that binds to a central metal ion. Overall the charge may be pos, neg or neutral.
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Which way do electrons move in electrolysis?
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Anticlockwise up from the positive electrode to the negative electrode
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Which side do the positive ions (metal ions) go to in electrolysis?
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The anode.
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What can change the experimental value of a theoretical EMF for a galvanic cell?
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Whether the electrodes are clean.
The molarity of the solutions. If they are both 0.1M, then the EMF should be 1/10th of the theoretical EMF. |
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What is electrolysis?
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A process in which an electric current is used to bring about chemical reactions that do not occur spontaneously.
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What does the voltage source do to the right hand electrode?
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It pulls electrons out of it to make that electrode positive.
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Which electrode in electrolytic cells is positive and why?
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The anode is (on the right). Because negative ions are oxidised at this electrode.
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Why does sulphate not get oxidised at the anode in an electrolytic cell?
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Because it is more stable than the water molecules and as a result the water molecules are oxidised.
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Where is the anodic site in rusting?
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The site where Iron is being oxidised
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Why does rusting occur more rapidly in salt water?
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Because the salt water is a better conductor than fresh water. Therefore ions flow faster through it.
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Why does stress increase the speed of rusting?
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Because Fe2+ ions break away more easily from the stressed crystal structure.
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What is galvanisation?
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Covering iron or steel with a layer of zinc in order to prevent rusting.
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Why does zinc work as a galvanisating metal?
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Because it is passivating, it forms a protective layer of Zinc hydroxide or carbonate.
Also it is more electronegative which means that it reacts with any Fe2+ to form Fe(s) again and also forms Zn(OH)2 which covers any scratches. |
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What is galvanisation also known as?
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Cathodic protection
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What is a sacrificial anode?
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A block of a more electronegative metal that corrodes more readily than iron or steel.
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Why does any Fe2+ formed return to Fe(s) when galvanisation or sacrificial anodes are used?
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Because the electrons given away by the more electronegative return the Fe2+ to solid Fe.
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