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What is a mole?

Rather than the furry creature, in chemistry a mole is a unit used to measure substances. Its equivalent to 6x10 23 atoms, the number of carbon atoms in 12g of carbon. To find a mole of a substance we use th...
JD
Answered by Jessica D. • Chemistry tutor
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Explain why Aluminium and Sulfur do not fit the expected trends of first ionisation energies of period 3?

Firstly, we should define the first ionisation energy The first Ionisation Energy is the energy required to remove one mole of electrons from one mole of gaseous atoms to form a mole of gaseous ions, each wi...
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Answered by Jake G. • Chemistry tutor
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Explain how electricity is conducted through a metal. To gain full marks your answer must include a description of the structure and bonding in a metal.

Metals can be described as a lattice of close-packed positive ions in a sea of delocalised electrons. Because the electrons are delocalised, they can move freely through the metal.
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Answered by Andrew B. • Chemistry tutor
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Which direction would the equilibrium move if the pressure at which a reaction takes place was increased? (Le Chatelier's Principle)

Looking at the reaction between hydrogen and carbon monoxide to form methanol: CO + 2 H 2 ⇌ CH 3 OH There are 3 moles on the left hand side and 1 mole on the right hand side. According to Le Chatelier's Prin...
EC
Answered by Ethan C. • Chemistry tutor
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Explain which species is oxidised in this reaction: Br2 +2I– = 2Br– +I2

A useful way to answer oxidation/reduction questions is to remeber the acronym OIL RIG: O xidation I s L oss (of electrons) R eduction I s G ain (of electrons) In this example Iodine is going from 2I- to I2 ...
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Answered by Rory B. • Chemistry tutor
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