Brønsted-Lowry Theory Essay

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Brønsted–Lowry

Left hand side: Johannes Nicolaus Brønsted (1879 - 1947)
Right hand side: Thomas Martin Lowry (1874 - 1936) THEORY
An acid is a proton (H+) donor
A base is a proton (H+) acceptor
EXPLANATION OF THE THEORY: Acids are proton donors and bases are proton acceptors. A hydrogen ion is the same thing as a proton since hydrogen consists of a proton and an electron. When hydrogen loses an electron all that is left is a proton.
According to the Brønsted-Lowry theory of acids and bases, when an acid and a base react, a conjugate base and a conjugate acid will be produced.
EXP: acid + base à conjugate acid+ conjugate base
EXP: HCl (aq)+NH3 (aq) à NH4+(aq)+ Cl-(aq) The conjugate acid (NH4+) is the acid formed when the base gains a hydrogen proton.
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An example of the Arrhenius theory's limits is the reaction which occurs when ammonia (NH3) reacts with water.
Ammonia+water → ammonium + hydroxide
EXP: NH3 + H2O → NH4+ + OH-
The Arrhenius theory does not consider ammonia a base. That is because when it is in water, it doesn’t contain or produce hydroxide ions. This is because NH4OH does not exist in reality. Therefore, since ammonia does not produce hydroxide when dissolved in water, it cannot (using the Arrhenius theory) be considered a base.
The Bronsted-Lowry theory is able to explain the result of the reaction because it defines acids and bases as proton donors and acceptors respectively. The theory also states that substances such as water are amphoteric which explains why it donates and accepts protons in certain reactions.
What occurs is that ammonia acts as a base and accepts the proton which the water molecule donates. Hydroxide is produced because water donated its H+ ion and only OH- is left. With the Bronsted-Lowry theory, certain compounds which don’t produce hydroxide or hydrogen when in a solution can be counted as acids and

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