Chemistry, Third edition

REVISION QUESTIONS 429

Revision questions

23.1.The following table shows the concentration of

strychnine in the blood at various times. (Measurements

started as soon as possible after hospital admission of the

patient).

Time from Strychnine

ingestion h concentration/mg dm –3

16.0 1.02

18.0 0.93

20.0 0.85

24.0 0.71

26.0 0.65

30.0 0.54

32.0 0.49

34.0 0.45

36.0 0.41

38.0 0.37

40.0 0.34

51.0 0.20

Estimate (i) the half-life of strychnine in the blood, (ii) the

concentration of strychnine in the patient at t= 0.

23.2.For the equilibrium

ethanol in breath ethanol in blood

it is found that a concentration of 35 g of ethanol per 100

cm^3 ofbreathcorresponds to 80 mg per 100 cm^3 ofbloodat

25°C. Use this data to calculate the molar concentration ratio:

[ethanol in blood]

[ethanol in breath]

23.3.(i)A man is suspected of being involved in a drink

related road accident. The blood alcohol concentration in the

subject two hours after the accident was 79 mg per 100 ml of

blood. Estimate the blood alcohol concentration at the time

of the accident.

(ii)The concentration of alcohol in urine is about 1.34 times

that of blood. The concentration of alcohol in saliva is about

9% higher than that of blood. Calculate the urine and saliva

alcohol concentrations in man with a blood alcohol concen-

tration of 80 mg per 100 ml.

23.4.(i)We have already noted that ethanol is converted

intoethanal(CH 3 CHO) in the body. It is also observed that

the consumption of ethanol causes the kidneys to eject more

acidic waste from the body. What does this suggest is the fate

of ethanal?

(ii)The structure of cocaine is:

(a)How many carbonyl groups (C=O) are present in

cocaine?

(b)What is the molecular formula of cocaine?

(c)What is the molecular mass of cocaine?

(d)The IR spectrum of cocaine contains an intense peak at

about 1700 cm–1. Explain this.

(e)The mass spectrum of cocaine shows a peak at m–e= 303.

What ion causes this peak?

23.5.The IR spectrum of liquid ethanol is shown above:

The spectrum of ethanol vapour is similar. Study the spec-

trum and identify two peaks that you think may be used to

measure the ethanol concentration in breath. Will (a) the

absorbance (b) the % transmittance of the peaks be pro-

portional to C 2 H 5 OH concentration?

23.6.A person is arrested by police and taken to the police

station where the alcohol concentration in her breath is

measured as equivalent to 100 mg ethanol per 100 ml of

blood. (a) What official statement of alcohol concentration

would be made by a forensic scientist? (b) Estimate the BAC

three hours after the measurement.

Extension material to support this unit is available on our website. See especially Case Study 2 on the

website.

NCH 3

OCOCH 3

OCO

CH 3 CH 2 OH

C—H

bend

(CH 2 and CH 3 )

C—H

stretch

(CH 2 and CH 3 ) C—O C—Hbend

bend

O—H

bend

O—H

stretch

(hydrogen-bonded alcohol)

4000 2000 1000 600

Wavenumber/cm–1

Transmittance/%

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