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The molar mass of caffeine is 194.19 g. Is the molecular formula of caffeine $\mathrm{C}_{4} \mathrm{H}_{5} \mathrm{N}_{2} \mathrm{O}$ or $\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{N}_{4} \mathrm{O}_{2} ?$

C8H10N402

Chemistry 101

Chapter 3

Mass Relationships in Chemical Reactions

Chemical reactions and Stoichiometry

Carleton College

Rice University

Drexel University

University of Toronto

Lectures

04:02

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity. Chemical reactions are usually characterized by a chemical change, and they yield one or more products after the reaction is complete. Chemical reactions are described with chemical equations, which symbolically present the starting materials, end products, and sometimes intermediate products and reaction conditions. Chemical reactions happen at a characteristic reaction rate at a given temperature and chemical concentration. Typically, reaction rates increase with increasing temperature because there is more thermal energy available to reach the activation energy necessary for breaking bonds between atoms.

08:02

In chemistry, a combination reaction is a chemical reaction in which two or more reactants combine to form more than one product. In a decomposition reaction, one reactant splits into two or more products.

02:22

The molar mass of caffeine…

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in this video, we're going to work on how to determine the molecular formula of a convent. We're going to do this by looking at the molar mass of caffeine and determining which of these two formulas accurately represent caffeine. To do this, we need Teoh. Calculate the molar mass of each of these two formulas and see which one matches up to the Miller Massive Caffeine, which is 194.19 Calculate the molar mass of each of these formulas. We need to know the molar mass of each individual element inside of the formulas. I have listed the molar masses here, and you can find them on a periodic table. Start. We're going to calculate the molar mass of the formula on the left. We do this by multiplying the molar mass of carbon by four because it is C four in adding the molar mass of hydrogen times five represented by age five, the molar mass of nitrogen by two and to and adding the molar mass of oxygen. When we calculate this out, we find out that the molar mass of the formula on the left is 93.6304 Obviously, this does not match up to the molar mass of caffeine 1 94.19 So the formula on the left cannot be caffeine. We then do the same thing. On the right side, we multiply the molar mass of carbon by eight molar mass of hydrogen by 10 the molar mass of nitrogen by four and the molar mass of oxygen by two. This gives us a molar mass of 1 94.19 for this formula. Obviously, this directly matches the Moeller massive caffeine we've been given. This means that the formula on the right is the formula for caffeine, and the formula on the left is not.

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