PHAR 205OLD EXAM

Answer the following questions

I- Circle the correct answer in the following questions below (40pts)

1) What is the total length of two pieces of tubing which measure 4.50 cm and

3.222 cm? Express the answer to the correct number of significant figures.

a) 7.72 cm b) 4.72 cm c) 7.722 cm d) 7.7 cm e) 8 cm

2) A laboratory technician reports that the mass of a growth removed from a

patient is 274.060 g. How many significant figures does this measurement contain?

a) 3 b) 4 c) 5 d) 6 e) none of the above

3) Find the ratio between two masses measured as 123.60 grams and 115.972

grams. Express the answer to the correct number of significant figures.

a) 1.0657 b) 1.066 c) 1.065 d) 1.0660 e) 1.07

4) The number of significant figures in 0.00230300 m is

a) 6 b) 9 c) 3 d) 4 e) 8

5) Aqueous solutions of the following species are prepared. In which case will the

resultant solution be acidic?

a) Na2O b) NH3 c) NO2- d) C2H5OH

6) Each of the following species is added to water. In which case will a basic

solution result?

a) NH4+ b) HCN c) HCl d) SO4

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7) If 1.82g of NaCN (M = 49 g.mol-1 ; Ka = 6.2 x 10-10) are dissolved in water and

additional water is added until the volume of resultant solution is 250mL, the pH of

the solution is

a) 2.81 b) 8.98 c) 2.48 d) 11.19

8) What will be the pH of 2 Liters of a buffer solution of 0.15M HF and 0.1M NaF (Kb = 1.47 x 10-11) after the addition of 50 mL of 0.05 mol/L NaOH

a) 2.95 b) 3.00 c) 3.34 d) 10.66

9) Calculate the pH of a solution prepared by mixing 25.0 mL of 0.212 M NaOH

and 36.0 mL of 0.187 M HCl

a) 1.63 b) 1.43 c) 3.34 d) 1.40

10) Calculate the pH of a solution prepared by mixing 400 mL of 0.100 M NH3 and

250 mL of 0.120 M HCl. (Ka of NH4Cl = 5.6 x 10-10)

a) 1.63 b) 8.77 c) 6 d) 5.22

II- Round each value to the given number of significant digits. (8 pts)

(a) 62 091 to three significant digits

(b) 27 to one significant digit

(c) 583.8 to one significant digit

(d) 0.590600 to three significant digits

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IV- A titration is performed by adding 0.200 M NaOH to 24 mL of 0.350 M HOCl.

( Ka = 3.5 x 10-8) (12pts)

i) Calculate the pH before addition of any NaOH.

ii) Calculate the pH after the addition of 5.0 mL of the base.

iii) Calculate the pH after the addition of 50 mL of the base

V- Explain why EDTA is titrated at high pH?

VI- A 50.00 mL sample of well water was transferred to a clean Erlenmeyer flask. Then, about 5 mL of ammonia buffer and a few drops of Eriochrome black T indicator were added. The sample was then titrated with the above EDTA solution (0.02500 M) and 15.38 mL was required for the color to change from red to blue. Determine the hardness of the well water, expressed as ppm of CaCO3 (M = 100.09)

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