Math Without a Calculator for AP Chemistry

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Verity Stone
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1 Math Without a Calculator for AP Chemistry Number Sense Let fractions be your friends! Fraction Decimal Percent 3/ 0.80 Example: / % % of % % of

2 Fermi Estimation Rules 1. Round all values to one significant digit 2. Divide numerator and denominator by any obvious common factor, especially power of ten 3. Combine factors in the denominator and factors in the numerator, by multiplying, except for 100. Apply the Fermi estimation rules to approximate the following: No calculator! Writing large or small numbers in scientific notation can vastly simplify operations ? 32 10? ? ? 2

3 Remember these exponent rules: a m a n a m+ n a m n m n m n m n a a ( a ) a ( 10-2 ) ( 10 - ) ( ) 2 ( ) ( ) ( ) ( ) ( ) (0.000) 2 ( ) 2 ( ) 2 x x.0 10 x

4 Sample Multiple Choice questions 1. What is the maximum mass of copper that could be plated out by electrolyzing aqueous CuCl 2 for 16.0 hours at a constant current of 3.00 amperes? A) 28 grams B) 7 grams C) 64 grams D) 114 grams E) 128 grams 2. How many grams of Na 2 CO 3 (molar mass g/mol) are required for complete reaction with 2.0 ml of 0.1 M HNO 3? Na 2 CO 3 (aq) + 2HNO 3 (aq) à 2NaNO 3 (aq) + CO 2 (g) + H 2 O (l) a) g b) 20 g c) 0.20 g d) g 3. Enough water is added to 11. grams of ethanol, C 2 H OH, to make 2.00 liters of solution. What is the molarity of the ethanol? a) 0.12 b) 0.20 c) 0.00 d).7 e) We have the following equilibrium: 2A B. At equilibrium we measure [A] 0.06 M and [B] 0.21 M. Calculate the equilibrium constant for the reaction as written. a) 67 b) 0.01 c) 3.8 d) 14. Calculate the volume, in milliliters, of 0.200M H 3 PO 4 required to completely neutralize 2.0 ml of 0.00M KOH. a) 20.8 ml b) 2.0 ml c) 0.0 ml d) 62.4 ml e) 7.0 ml 6. A compound containing only carbon and hydrogen is 80.0% by weight carbon. Which of the following represents the empirical formula for the hydrocarbon? a) CH b) CH 2 c) C 2 H 3 d) CH 3 4

5 7. Approximately what mass of CuSO 4 H 2 O (20 g mol - 1 ) is required to prepare 20 ml of 0.10M copper(ii) sulfate solution? a) 4.0 g b) 6.2 g c) 34 g d) 8 g 8. A 14.0 L cylinder contains.60 g N 2, 40.0 g Ar, and 6.40 g O 2. What is the total pressure in atm at 27⁰C? A) 26 x B) 30 x C) 60 x D) 120 x In the figure there are three gases present, Gas A, B, and C the number of spheres represents the number of moles of each gas present. If the total pressure within the vessel is.0 atm, what is the partial pressure of Gas B? A) 1.00 atm B) 1.33 atm C) 1.0 atm D) 1.67 atm 10. Each of the following salts has a solubility of 1.0 x 10 - M. Rank the salts in order of lowest to highest Ksp. AX B 2 X C 2 X 3 D 3 X A) C 2 X 3 < D 3 X < B 2 X < AX B) C 2 X 3 < D 3 X < AX < B 2 X C) D 3 X < C 2 X 3 < B 2 X < AX D) D 3 X < B 2 X < AX < C 2 X In a saturated solution of Zn(OH) 2 at 2⁰C, the value of [OH - ] is 2.0 x 10-6 M. What is the value of the solubility product constant, Ksp, for Zn(OH) 2 at 2⁰C? A) 4.0 x B) 8.0 x C) 4.0 x D) 2.0 x Consider N 2 (g) + O 2 (g) 2 NO (g). The reaction was initiated by adding 1.0 moles of NO to a 1.0- L flask. At equilibrium, 3.0 moles of oxygen are present in the 1.0- L flask. Calculate the value of Keq. A) 0.33 B) 3.0 C).0 D) 9.0

6 mol NaC 2 H 3 O 2 and 0.00 mol HCl was added to 1.0 L of 0.07 M HC 2 H 3 O 2. List the species in order of decreasing equilibrium concentration. A) [HC 2 H 3 O 2 ] > [C 2 H 3 O 2 - ] > [Cl - ] > [H 3 O + ] B) [H 3 O + ] > [Cl - ] > [C 2 H 3 O 2 - ] > [HC 2 H 3 O 2 ] C) [HC 2 H 3 O 2 ] [C 2 H 3 O 2 - ] > [Cl - ] [H 3 O + ] D) [Cl - ] [H 3 O + ] > [HC 2 H 3 O 2 ] [C 2 H 3 O 2 - ] 14. Consider the equilibrium H 2 (g) + I 2 (g) 2 HI (g) In a closed system, the initial partial pressure of hydrogen is 1.2 atm and the initial partial pressure of iodine is 1.7 atm. At equilibrium, the partial pressure of hydrogen is 1.00 atm. Which expression gives the value of Kp for this system? A) (0.0) 2 C) (0.0) 2 (1.00) (1.7) (1.00) (1.0) B) (0.2) 2 D) (0.2) 2 (1.2) (1.7) (1.00) (1.0) 1. What is the enthalpy change for the following reaction under standard conditions? CS 2 (l) + 2 O 2 (g) à CO 2 (g) + 2 SO 2 (g) ΔH⁰ f CS (l) +88 kj/mol ΔH⁰ f CO 2 (g) 394 kj/mol ΔH⁰ f SO 2 (g) 297 kj/mol A) 1076 kj/mol B) 900 kj/mol C) 779 kj/mol D) 603 kj/mol 16. Consider the reaction C 2 H OH(l) + 3 O 2 (g) à 2 CO 2 (g) + 3 H 2 O(l) ΔH x 10 3 kj/mol When a 1.1 g sample of ethyl alcohol (molar mass 46.1 g/mol) is burned, how much energy is released as heat? A) kj B) 2.2 x 10 3 kj C) 4.49 x 10 2 kj D) 1.02 x 10 3 kj 6

Chemistry Stoichiometry and Heat Exam (ver.1) Mr. Thaler. Please do not write on this exam. Mark your answers on the scantron only.

Chemistry Stoichiometry and Heat Exam (ver.1) Mr. Thaler. Please do not write on this exam. Mark your answers on the scantron only. 1. Identify from the unbalanced equations below the one that does not represent a redox reaction. a. H 2O 2(aq) + MnO 4 - (aq) O 2(g) + Mn 2+ (aq) b. H 2(g) + N 2(g) NH 3(g) c. NaCl (aq) + AgNO 3(aq) NaNO