Chemical Analysis

Chemical Analysis Activity:

Ø Introduction (equilibrium):

Question 1

Write each answer with the correct number of digits:

a) 3.021 + 8.99 =

d) 0.0302÷(2.1143×10^-3) =

b) 12.7 – 1.83 =

e) log (2.2×10^-18) =

g) 10^-4.555 =

c) 6.345×2.2 =

f) antilog (–2.224) =

Question 2

Find the absolute and percent relative uncertainty and express each answer with a reasonable number of significant figures:

a) 3.4 (±0.2) + 2.6 (±0.1) =

b) [3.4 (±0.2)×10-8]÷[2.6 (±0.1)× 103] =

c) 3.4 (±0.2)÷2.6 (±0.1) =

d) [3.4 (±0.2) – 2.6 (±0.1)]×3.4 (±0.2) =

Question 3

a) A solution is prepared by dissolving 0.2222 (±0.0002) g of KIO₃ [FM 214.0010 ±0.0009] in 50.00 (±0.05) mL. Find the molarity and its uncertainty with an appropriate number of significant figures.

b) Would the answer be affected significantly if the reagent were only 99.9% pure?

Question 4

Using activity coefficients correctly, calculate the pH of

a) 0.050 M HBr

b) 0.050 M NaOH

Question 5

Find the pH and fraction of dissociation (α) of a 0.010 0 M solution of the weak acid HA with

K_a = 1.00×10^-4.

Question 6

A 0.100 M solution of the weak acid HA has a pH of 2.36. Calculate pKa for HA.

Question 7

Calculate the concentration of Tl⁺ in a saturated solution of TlBr in water (K_sp = 3.7 x 10^-9). Include activity effects.

a) Calculate the concentration of Tl⁺ in a saturated solution of TlBr in 0.9 % w/v NaCl solution. Include activity effects.

b) Comment on the difference between you answers to a) and b) above.

Questions 8:

a. Why do we worry about significant figures?

b. What do we mean by the term ‘ionic strength’ and ‘activity’? What are these things important? What are the implications for solutions?

c. What happens to the amount of ionisation as we increase the ionic strength of a solution? What happens to the solubility of a salt?

d. What is meant by the various terms we use when discussing analytical techniques?

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Ø Chemical Analysis Activity – Introduction to Spectroscopy:

Question 1

List some applications for the following spectroscopic methods. In each case give reasons why the method is most suitable for the given application:

a) HNMR spectroscopy:

b) Florescence spectroscopy:

c) Atomic emission spectroscopy:

d) XRF spectroscopy:

Question 2

Calculate the energy range of photons in:

a) The X-Ray region of the spectrum:

b) The visible region of the spectrum:

c) UVA, UVB and UVC. Which part of the UV spectrum is most damaging to skin? Why?

Question 3:

a) Describe what happens to a molecule when it absorbs IR radiation.

b) Do all molecules absorb IR radiation? Why/Why not?

c) When you go outside on a sunny day you feel the warmth of the sun – what is responsible for this?

Questions 4:

a. What do we mean by the term ‘spectroscopy’?

b. Give examples of the spectroscopic techniques mentioned in this Module. What are some applications of each?

c. What is the difference between ‘molecular’ and ‘electronic’ spectroscopy? Give examples of both.

d. What happens when an atom or molecule absorbs radiation? What are the possible fates of those atoms or molecules? Give examples.

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Ø Chemical Analysis Activity – IR Spectroscopy:

Question 1

For each of the following IR spectra indicate which of the five given compounds is responsible for the spectrum. You must be choice one compound for each spectrum with your explanation.

Answer:

Answer:

Question 2

Each of the IR spectra shown below is the spectrum of one of the following compounds. Identify the compound that is responsible for each spectrum.

Answer: