Physical Chemistry

Reversible Reactions, Equilibrium, and Le Chatelier’s Principle

Infographic on equilibrium and Le Chatelier's principle. Equilibrium is reached when a reaction's forwards and backwards rates are equal. Le Chatelier's principle states that when a change is made to the conditions of a dynamic equilibrium the system counteracts the change, changing the quantities of reactants and products. Increasing concentration of substances on one side of the reaction will increase the concentrations of substances on the other side. Increasing temperature favours the endothermic reaction, while decreasing it favours the exothermic reaction. And increasing pressure favours the side of the reaction with fewer gas molecules.
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When you think of chemical reactions, you might think of them as irreversible, permanently changing one substance into another. While this is true in some cases, some chemical reactions are reversible, and we can take the products of the reaction and turn them back into the reactants. These reversible reactions can, under certain conditions, reach what we call ‘equilibrium’. Equilibrium can be a tricky concept to understand, but this graphic tries to make it a little clearer.

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The Secrets of the Coke and Mentos Fountain

The Secrets of the Coke and Mentos Fountain

The Secrets of the Coke and Mentos Fountain
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It’s one of the most popular science demonstrations: Pop a handful of Mentos candies into a bottle of Coke, and a fountain of bubbles rapidly spurts from the open bottle, often over a metre into the air. Originally the explanation for the effect was thought to be quite simple. However, scientists are finding that there’s more to this spectacular demonstration than meets the eye.

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Today in Chemistry History – Ernest Rutherford’s Birthday

Today in Chemistry History: Ernest Rutherford's birthday. Shows a picture of Rutherford with a short bio: he won a Nobel Prize in Chemistry for work on radioactivity, naming alpha and beta radiation. He also developed the Rutherford model of the atom. A diagram shows his famous gold foil experiment, in which alpha particles were fired at thin metal foils. Most passed through the foil but a small number were deflected back at a large angle. This showed that the positively charged protons are concentrated in the nucleus of the atom.
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Today, 30 August, marks the birthday of Ernest Rutherford. Rutherford is primarily considered a physicist, but his contribution to our understanding of the atom is also important to chemistry. He was also a chemistry Nobel Prize winner, for his work on radioactivity. This graphic looks in detail at one of his most famous experiments, the gold foil experiment which is often name-dropped in school science lessons!

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