Study Guides (248,570)
Canada (121,626)
York University (10,209)
Chemistry (3)
CHEM 1AA3 (3)
all (3)
Midterm

[Exam Tutorial] Chem 1AA3 Fall 2012 Term Test 1 Questions

10 Pages
141 Views
Unlock Document

Department
Chemistry
Course
CHEM 1AA3
Professor
All Professors
Semester
Winter

Description
VERSION 1. Enter your version number in the correct column on your scan sheet (see p.2 for details) 1. The pH of a 0.01 M aqueous solution of a strong base is: A) 3 B) 13 C) 12 D) 1 E) 7 2. Which of the following combinations of aqueous solutions would give a buffer? (All solutions are 1.0 M). A) 10 mL HClO + 40mL KClO 2 B) 15 mL HClO + 45mL KClO 4 C) 20 mL HClO + 40mL KOH D) 20 mL HClO + 20mL KClO 4 E) 10 mL HClO + 20mL KOH 3. Which of the following compounds will produce a basic solution when placed into water? (i) Na2O (ii) N4 Cl (iii) LiBr (iv) CH3COOK (v) CH 3H 2 A) iii, v B) i, ii C) ii, iii, iv D) ii, iv E) i, iv, v 4. MES is a common buffer in chemical biology. At pH 6.5, the ratio of MES, a weak base, to irs conjugate acid, MESH , is [MES]/[MESH ] = 2.19. What is the pK of MESH ? + a A) 7.17 B) 7.47 C) 6.76 D) 5.65 E) 6.16 5. Which of the following statements about buffers is false? A) The percent ionization of the weak acid or weak base in a buffer is negligible (close to zero) B) Weak acid-strong base titration curves show a buffer region right up until the equivalence point. C) Buffers resist changes in pH by converting strong base into weak base, or strong acid into weak acid. D) The buffer capacity for a weak acid (HA)/weak base (A ) system is at a maximum - when [HA] and [A] are equal. E) A buffer’s capacity can be exceeded by adding excess amounts of strong acid. + 6. What is [H O 3 (in M) in 1.0 M CH COOH(3q)? Data: K aCH C3OH) = 1.8 x 10 -5 -3 A) 1.66 x 10 -3 B) 1.34 x 10 C) 3.22 x 10 -3 -3 D) 4.24 x 10 -3 E) 7.18 x 10 7. A buffer is made using only Tris (weak base) and TrisHCl (weak acid). What mass (in g) of solid TrisHCl would be used to make 0.20 L of a buffer solution with a total buffer concentration ([Tris] + [TrisH ]) of 0.050 M, and pH 7.80? TrisH + H O 2 Tris + H O 3 + Data: + pK aTrisH ) = 8.30 mol wt(TrisHCl) = 157.6 g/mol mol wt(Tris) = 121.1 g/mol A) 10.5 B) 2.80 C) 1.20 D) 1.50 E) 0.80 8. What is the pH of the solution that results when the following substances are added to water to create 1.00 L of solution? 0.100 mol HNO 3 0.100 mol HNO 2 0.300 nol NaNO 2 Data: -4 Ka(HNO ) 2 7.2 x 10 A) 3.53 B) 4.65 C) 6.04 D) 2.30 E) 3.14 9. Bromophenol blue is an acid-base indicator with a pK of 4.0. The acidic form is yellow a and the basic form is blue-violet. A few drops of this indicator are added to the titration of benzoic acid (beaker, pK a 4.20) with NaOH(aq) (buret). Find the false statement(s) about this titration experiment. (i) The indicator starts to change from yellow to blue-violet at about pH 3 and completes the change from to blue-violet at about pH 5. (ii) The indicator will be yellow over the entire buffer region of the titration curve. (iii) The bromophenol blue indicator is not an appropriate choice for locating the equivalence point of this titration. A) No statements are false B) i C) ii D) iii E) i, iii 10. Which would be the best pH indicator to find the endpoint in a titration of 0.050 M cacodylic acid with 1.100 M LiOH? (Cacodylic acid is a monoprotic acid.) Data: -7 K acacodylic acid) = 5.7 x 10 Indicator Colour change range (pH) A) Methyl orange 3.1 – 4.4 B) Thymolphthalein 9.3 – 10.5 C) Cresol red 7.2 – 8.8 D) Bromophenol blue 3.0 – 4.6 E) Bromophenol blue 6.0 – 7.6 11. Some parts of human cells, like the endosomes, are acidic, with pH ≈ 5.5. Which of the following weak acids would be the most effective acid component of a buffer to maintain pH 5.5 (assuming equal concentrations of all buffers)? Weak acid Ka A) glycine 4.6 x 10 -3 B) lactic acid 1.4 x 10 -4 C) H PO - 6.3 x 10 -8 2 4 -7 D) H 2O 3 4.5 x 10 + -10 E) NH 4 5.5 x 10 12. If the pH indicator cresol red (yellow at low pH, purple at high pH) is placed in a buffer solution with pH 7.40, what percenta
More Less

Related notes for CHEM 1AA3

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit