AP Chemistry 1980 Free Response Questions

AP Chemistry 1980 Free Response Questions - 1980 Free...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
1980 Free Response Questions 1) Methylamine, CH 3 NH 2 , is a weak base that ionizes in solution as shown by the following equation. CH 3 NH 2 + H 2 O <===> CH 3 NH 3 + + OH¯ (a) At 25 °C, the percentage ionization in a 0.160-molar solution of CH 3 NH 2 is 4.7%. Calculate [OH¯], [CH 3 NH 3 + ], [CH 3 NH 2 ], [H 3 O + ], and the pH of a 0.160-molar solution of CH 3 NH 2 at 25 °C. (b) Calculate the value for K b , the ionization constant for CH 3 NH 2 , at 25 °C. (c) If 0.050 mole of crystalline lanthanum nitrate is added to 1.00 liter of a solution containing 0.20 mole of CH 3 NH 2 and 0.20 mole of its salt CH 3 NH 3 Cl at 25 °C, and the solution is stirred until equilibrium is attained, will any La(OH) 3 precipitate? Show the calculations that prove your answer. (The solubility product constant for La(OH) 3 , K sp , is 1 x 10¯ 19 at 25 °C. 2) M(s) + Cu 2+ (aq) ---> M 2+ (aq) + Cu(s) For the reaction above, E° = 0.740 volt at 25 °C. (a) Determine the standard electrode potential for the reaction half- reaction M 2+ (aq) + 2 e¯ ---> M(s).
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
(b) A cell is constructed in which the reaction above occurs. All substances are initially in their standard states, and equal volumes of the solutions are used. The cell is then discharged. Calculate the value of the cell potential, E, when [Cu 2+ ] has dropped to 0.20 molar. (c) Find the ratio [M 2+ ] aq / [Cu 2+ ] aq when the cell reaction above reaches equilibrium. 3) (a) A solution containing 3.23 grams of an unknown compound dissolved in 100.0 grams of water freezes at -0.97 °C. The solution does not conduct electricity. Calculate the molecular weight of the compound. (The molal freezing point depression constant for H 2 O is 1.86 °C kg mole¯ 1 .) (b) Elemental analysis of this unknown compound yields the following percentages by weight: H = 9.74%; C = 38.70%; O = 51.56%. Determine the molecular formula of the compound. (c) Complete combustion of a 1.05-gram sample of the compound with the stoichiometric amount of oxygen gas produces a mixture of H 2 O(g) and CO 2 (g). What is the pressure of this gas when it is contained in a 3.00-liter flask at 127 °C? 4) Answer FIVE of the eight options in this part. (Answer to more than five options will not be scored.) (a) Solutions of sodium fluoride and dilute hydrochloric acid are mixed.
Background image of page 2
(b) A saturated solution of barium hydroxide is mixed with a solution of iron(III) sulfate. (c) A solution of ammonium sulfate is added to a potassium hydroxide solution. (d) Carbon dioxide gas is bubbled through a concentrated solution of sodium hydroxide. (e) Solid copper is added to a dilute nitric acid solution. (f) Chlorine gas is bubbled into a cold solution of dilute sodium hydroxide. (g) A solution of potassium permanganate is mixed with an
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 09/03/2011 for the course CHM 2046 taught by Professor Haces during the Spring '11 term at FAU.

Page1 / 15

AP Chemistry 1980 Free Response Questions - 1980 Free...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online