SAT Subject Test Chemistry,10 edition

(Marvins-Underground-K-12) #1

In question 10, if the temperature of an exothermic reaction is increased, the reaction shifts to the
left. If the temperature of an endothermic reaction is increased, it shifts to the right. The reaction
has a negative enthalpy of reaction, meaning that it is an exothermic reaction. If the temperature of
this reaction is increased it will be shifted to the left, making choice B correct.


For question 11, the equilibrium constant is the ratio of the concentration of the products to the
concentration of the reactants for a certain reaction at equilibrium, all raised to their stoichiometric
coefficients. Properties of the equilibrium constant include: Pure solids and liquids do not appear in
the equilibrium constant expression; Keq is characteristic of a given system at a given temperature; if
the value of Keq is very large compared to 1, an equilibrium mixture of reactant and products will
contain very little of the reactants compared to the products; if the value of Keq is very small
compared to 1, an equilibrium mixture of reactants and products will contain very little of the
products compared to the reactants. So, choice B is correct.


In the exothermic equation (negative ∆H) in question 12, 30 kJ/mole is given off. If one mole of N 2
produces 30 kJ/mole, then 1.5 moles of N 2 will produce 1.5 (30 kJ/mole), which equals 45 kJ, choice
A.


To answer question 13, you need to investigate the Brønsted-Lowry definition of acids and bases.
The Brønsted-Lowry acid is a species that donates protons, while a Brønsted-Lowry base accepts
protons. For example, NH 3 and Cl– are both Brønsted-Lowry bases because they accept protons.
They are not Arrhenius bases because they do not produce OH– in aqueous solutions. The advantage
of the Brønsted-Lowry concept of acids and bases is that it is not limited to aqueous solutions.
Choice D is correct.


(C) N 2     and NH 3
(D) NH 3
(E) All of them have basic qualities.
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