Portage Learning Chem 210 - Module 2 exam

Question 1 3 / 3 pts Scientific Calculator The pH of a solution of 8.9 x 10-12 M NaOH is: A. 8.9 B. 8.9 x 10-12 C. 4.8 D. 11 E. 2.9 A B C D Correct! E [Kw=[H+][OH-] = 1.0 x 10-14; [H+][8.9 x 10-12] = 1.0 x 10-14 ;[H+]=890; pH=-log[890]=2.9] Question 2 3 / 3 pts Water is a unique molecule. Which of the following contributes to water’s unique place in the chemical world? The geometry of the molecule The polarity of the O-H bonds The ability of water molecules to hydrogen bond The bond angle of water All of the answers are correct ALL OF THE ANSWERS ARE CORRECT What factor contributes to the bent shape of a water molecule? The dipole arrows in a water molecule The unshared electron pairs on the oxygen atom The electronegativity difference between hydrogen and oxygen The unequal electron sharing between hydrogen and oxygen None of the answers are correct THE UNSHARED ELECTRON PAIRS ON THE OXYGEN ATOM Question 4 3 / 3 pts Which diagrams correctly represent a hydrogen bond? A and B A and D B and C C and D A and C A AND C BOTH SHOW A PROTON DONOR AND ACCEPTOR Question 5 3 / 3 pts Scientific Calculator The H+ concentration of a solution is 5.6 x 10-5 What is the pH? -4.25 Correct! 4.25 [ [H+]=5.6 x 10-5; pH=-log[5.6 x 10-5]=4.25] 5.65 -9.75 9.75 4.25 [ [H+]=5.6 x 10-5; pH=-log[5.6 x 10-5]=4.25] If the Ka of an acid is 2.67 x 10-5, what is the pKa? 7.45 12.25 5.26 2.67 4.57 4.57 [pKa = -log(2.67 x 10-5) = 4.57] Question 7 3 / 3 pts List the acids in INCREASING order of strength (weakest to strongest): Nitrous acid (Ka = 4.0 x 10-4); acetic acid (Ka = 1.7 x 10-5); phosphoric acid (Ka = 7.3 x 10-3) Nitrous acid, acetic acid, phosphoric acid Acetic acid, nitrous acid, phosphoric acid Phosphoric acid, nitrous acid, acetic acid Acetic acid, phosphoric acid, nitrous acid None of the above ACETIC ACID, NITROUS ACID, PHOSPHORIC ACID