Methane is the compound CH4, and burning it uses the reaction:
CH4 + O2 -> CO2 + H2O, which is rather exothermic. To find the heat released by burning a certain amount of the substance, you should look at the bond enthalpy of each compound, and then compare the values before and after the reaction. In methane, there are 4 C-H bonds, which have bond energy of 416 kj/mol, resulting in a total bond energy of 1664 kj/mol. O2 is 494 kj/mol. Therefore we have a total of 2080 kj/mol on the left side. On the right side we have CO2, which has 2 C=O bonds, each at 799 kj/mol each, resulting in 1598 kj/mol, and H2O has 2 O-H bonds, at 459kj/mol each, resulting in a total of 2516 kj/mol on the right hand side. Now, this may be confusing because the left hand side seems to have less heat than the right, but you just need to remember: making minus breaking, which results in a total change of 436kj/mol heat evolved.
Now it is a simple matter of find the mols of CH4 reacted, using n=m/mr.
n = 9.5/16.042 = 0.592195 mol
Therefore, if we reacted 0.592195 mol, and we produced 436 kj for one mol, the total amount of energy evolved was 436*<span>0.592195 kj, or 258.197 kj.</span>
Answer:
Alchemy is a practice of making gold from other metals.
Explanation:
Alchemy is a method which is practiced by the ancient scientists of Europe, Africa and Asia trying to produced gold from other metals. This method was failed to produced gold from metals and all scientist suggested that metals can not be converted into gold. Greeks were the people who presented the theory of alchemy in the first few centuries of CE.
Answer:
Keto - enol tautomerism
Explanation:
Phenolphthalein is an organic molecule (formula: C20H14O4), which is used in to determine the final volume in an acid-base titration, this is, as the molecule changes from one to another color, depending on the Ph of the solution (in acids solution, the molecule remains colorless, while in basics solutions it remains pink) :
The molecule of phenolphthalein is a week acid, which losses a proton (H+) when it´s in solution: the undissociated molecule is colorless, while the correspondent anion (without a H+) is pink. This may be simplified with the following reaction:
H₃In⁺ ⇄ H₂In (colorless) ⇄ In⁻² (pink) ⇄ In(OH) ⁻³
- When adding a base (for example, NaOH) to phenolphthalein (initially, a colorless solution), molecule losses one H⁺ and we obtain In⁻², which is pink
- When adding an acid, the original structured is recovered, so color turns from pink to colorless
This change color is not only explained with adding an acid or a base, but also with phenolphthalein structure, that leads to a keto-enol tautomerism: as molecule has 2 hydroxyl groups (- OH) and 1 carbonyl group (C = O), compounds with this structure have an equilibrium between both groups:
R1 = C H– OH ⇄ R1 – C = O
With this change, phenolphthalein structure changes and hence, color solution changes as well
Answer:
The size of an isolated atom can't be measured because we can't determine the location of the electrons that surround the nucleus. We can estimate the size of an atom, however, by assuming that the radius of an atom is half the distance between adjacent atoms in a solid. This technique is best suited to elements that are metals, which form solids composed of extended planes of atoms of that element. The results of these measurements are therefore often known as metallic radii.
.Explanation:
