Tutor profile: Aly G.
Subject: SAT II Chemistry
Below is a students response to a quiz last year. There is an error in their attempt to balance the chemical equation. Please: 1. Identify the error and re-write the correctly balanced chemical equation 2. In a few sentences explain to the student how you determined the correct answer 2 C2H6 + 4 02 --> 6 H2O + 4 CO2
1. Correct equation: 2 C2H6 + 7 O2 --> 6 H2O + 4 CO2 2. In your original answer, the oxygen atoms were not balanced on each side. There were a total of 8 oxygen atoms in the reactants and 14 oxygen atoms in the products. It is possible that you only balanced the O2 molecule in the reactants with the oxygen atoms of CO2 in the products. However, the oxygen atoms in the H2O molecule on the product side also has to be considered. Since there is a total of 14 oxygen atoms on the product side, adding a coefficient of 7 in front of O2 on the reactant side balances the equation with 14 oxygen atoms on both sides.
Using Boyle's law, explain how we are able to drink water from a cup with a straw.
Boyle's law describes the inverse relationship between the volume and pressure of a gas when the temperature is held constant. This means that as the pressure decreases the volume will increase within a system. When we change the shape of our mouth to fit on the end of a straw, we are increasing the volume within our mouth. Based on Boyle's Law, this means that the pressure inside the mouth will decrease. Now the pressure in the straw is higher than that in the mouth, so air from the straw will start to flow into the mouth. This decreases the pressure within the straw, so now the atmospheric pressure outside of the straw is larger than that within the straw. This causes air in the atmosphere to push down on the water in the cup, which pushes it up the straw and into our mouths.
How did Darwin's contribution of the theory of evolution influence the understanding of human development?
Darwin suggested that individual members of a species who can overcome environmental demands are the ones that survive. This was not only limited to possessing necessary physical characteristics, but also necessary behavioral traits. Therefore, the western understanding of human development became focused on the adaptive function of human behaviors.
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