54 – 6 ÷ 2 + 6 = ? A. 6 B. 24 C. 27 D. 30 E. 57

To answer this question, we need to review the order of operations we use when solving problems. A helpful way to remember the order of operations is through the made-up word PEMDAS. P stands for parentheses, which we do first when solving problems. Then exponents, multiplication, division, addition, and subtraction in that order. In the problem above, we see division should be done first [6 ÷ 2 = 3]. Then, we can proceed to find the difference for 6 and 3, and the sum of 54 and 3, which brings us to an answer of 57, choice E.

Which of the following is the least? A. 0.105 B. 0.501 C. 0.015 D. 0.15

To help you see which decimal value is the least, we need to compare the largest place values first. All values have a 0 in the one's place. So we move on to the next highest place value: the tenths place. Choice C has the lowest value, 0, in the tenths place. Therefore, choice C is the least.

During a chemical reaction, what defines when the concentration of the reactants and products reach a constant level? A. elementary process B. reversible reaction C. rate law D. rate constant E. equilibrium

E. equilibrium [An elementary process expresses reaction mechanisms; A reversible reaction will help explain how two reactions are simultaneously occurring between reactants and products; A rate law provides a relationship between the rate of a reaction and reactant/product concentrations; A rate constant provides quantifiable data for the rate law relationship at a given temperature; Therefore, equilibrium is defined by the balance created when there are equal concentrations of products and reactants in a reaction