Moles and Stoich: Electrolysis Lab






Red: left   Blue: right


In the electrolysis lab today in chemistry we decomposed water into oxygen and hydrogen gas. This was done by mixing epsom salt into water and pouring this solution into two plastic tubes. these two tubes then where sealed tightly above the prongs of a tack inside of a medicine cup. The bottom of the tacks then where place on the leads of a battery allowing current to flow through the tack. The epsom salt acts as a catalyst as the current begins to separate water into hydrogen and oxygen. the reaction is shown below.  

2H2O(l) —-> 2H2(g) + O2(g)

Qualitative: This reaction is balanced and it is visible in the plastic tubes in two ways 1) The volumes of gas created by this reaction are clearly visible as the production of hydrogen gas is double of oxygen. This is because one mole of any gas fills the same amount of volume at STP and hydrogen has two moles while oxygen has one meaning hydrogen takes up twice as much space then oxygen. 2) we could prove that the plastic tube with twice as much gas contained hydrogen and the other tube oxygen because of the use of the universal indicator in the tubes. Before the reaction took place the two drops of a Ph indicator were placed in both tubes. As the reaction took place one tube turned red and the other blue, this was due to the splitting of hydrogen from the H2O molecule causing one tube to be more acidic and the other more basic. The tube with twice as much gas turned red indicating an acid and this means an abundance of H+ ions which causes compunds to have an acidic nature, and the other tube turned blue showing a basic nature which is characterized by OH- ions which when out of solution form into oxygen molecules.

Quantitative: Another way we could figure out if this equation was balanced would be through measurements. This would be done by measuring the initial mass of the the solution before reaction and comparing it to the mass of the gasses after the reaction is complete. The oxygen and hydrogen gasses should mass out to the mass of water in solution, also the masses of the gases would come out to 2 moles of hydrogen to every one mole of oxygen. Under the law of conservation of mass this way of measuring would prove that the reaction is balanced because no matter can be created or destroyed.

This particle diagram below shows the decomposition of water into hydrogen and oxygen gas. 




About chriscatanach

I enjoy long walks on the beach and watching the sun set. I am in a long term relationship with math and science. The movies are what I consider a man-made heaven. Most of all I think my self out to be the fictional reincarnation of Jay Gatsby.
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