Tutor profile: Meagan W.

Calculate the mass (in kg) of water produced from the combustion of 3.8 L of gasoline (C8H18). The density of gasoline is 0.79 g/mL.

To begin this problem, we need a balanced chemical equation. This is evidenced by the fact that we are given an amount of a reactant and are asked for the amount expected to be produced. Before we can write the balanced chemical equation, we need to determine what our reactants and products are. Since we know that the generic combustion reaction is organic molecule + O2 --> CO2 +H20 we can deduce that the chemical equation must be C8H18 + O2 --> CO2 +H2O. Now, we need to balance the equation. Right now we have 8 carbon, 18 hydrogen, and 2 oxygen on the left of the equation. On the right, we have 1 carbon, 2 hydrogen, and 3 oxygen.

Are two atoms of the same element always identical?

No, two atoms of the same element are not always identical. Some elements take on different forms, known as isotopes, where two atoms may have different numbers of neutrons from one another. For example, if we had a carbon atom, we would expect it to have 6 protons, neutrons, and electrons. However, there are isotopes of carbon used in radioactive dating of fossils that have 6 protons, 8 neutrons, and 6 electrons. There are other possible differences, but this is the most important for the scope of basic chemistry.

What is genetic drift and why is it important?

Genetic drift can be thought of as the opposite of natural selection. While they both are an explanation as to how allele frequencies change in a population over time, genetic drift refers to random chance events rather than the concept of survival of the fittest. The most common causes of genetic drift are natural disasters, such as fires, tornados, and flooding. Basically, one of these natural disasters will occur and wipe out a portion of the population regardless of how able they are to survive and reproduce in their environment. This causes changes in the traits being passed on to the next generation. Genetic drift is important because it is one of the five factors that drive evolution.