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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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What do I need to know about fractional distillation?

Fractional distillation is covered in almost every GCSE chemistry course, although what you need to know varies slightly by syllabus. The main points to take away are explained below. Why do we do fractional...
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Answered by Sophie V. • Chemistry tutor
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Calculate the percentage, by mass, of carbon in sodium hydrogencarbonate (NaHCO3)

When faced with this style of problem there are steps to correctly answer the quesion: Step 1 - identify the atomic mass of carbon Step 2 - calculate the atomic mass of the compound Step 3 - work out the per...
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Answered by Hayden T. • Chemistry tutor
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Aspirin C9H8O4 is made when salicylic acid C7H6O3 reacts with ethanoic anhydride C4H6O3 . The equation for this reaction is: C7H6O3 + C4H6O3 → C9H8O4 + CH3COOH Calculate the maximum mass of aspirin that could be made from 100 g of salicylic acid.

A relevant equation is: mass = moles x relative formula mass Also written: m = n*M r This reaction is a 1:1 ratio of salicylic acid to aspirin, meaning 1 mole of salicylic acid makes a maximum of 1 mole of a...
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Answered by Emma H. • Chemistry tutor
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What mass of carbon dioxide is produced from burning 100 grams of ethanol in oxygen according to this reaction: C2H5OH + 3 O2 --> 2 CO2 + 3 H2O

When approaching a question like this I always find it easier to write out the equation with the known quantities written underneath each individual compound. This allows us to easily check whether the equat...
KM
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