Ch 25 Q1 : Write a nuclear equation to represent

(1)

241 94

Ch 25

Q1 :

Write a nuclear equation to represent ^--particle emission by Pu.

Q2 :

131I is a ^- emitter used as a tracer for radioimmunoassays in biological systems.

Use information in Table 25.1 to determine (a) the decay constant in s^-1; (b) the activity of a 2.05 mg sample of ¹³¹I; (c) the percentage of ¹³¹I remaining after 16 days;

and (d) the rate of ^- emission after 16 days.

Q3 :

223Ra has a half-life of 11.4 days. How would it take for the activity associated with a sample of ²²³Ra to decrease to 1.0% of its current value?

(2)

Q4 :

What is the age of a mummy, given a ¹⁴C activity of 8.5 dis min^-1g^-1?

Q5 :

What is the energy associated with the a decay of ¹⁴⁵Sm(145.913053 u) to

142Nd(141.907719 u)?Use 4.002603 u as the mass of ⁴He.

(3)

Ch26

Q1 :

Write condensed structural formulas for the five constitutional isomers with the formula C6H14.

Q2 :

Give an IUPAC name for CH3CH2CH(CH3)CH2CH2C(CH3)2CH2CH3.(Hint: Any CH3

group enclosed in parentheses is bonded only to the C atom preceding it.)

Q3 :

Draw Newman projections for the staggered conformations of 2-methylpentane when the molecule is viewed along the C1---C2 bond. Rank the conformations in order of increasing energy (from lowest to highest).

(4)

Q4 :

Draw the lower energy conformation of trans-1,4-dimethylcyclohexane.

Q5 :

Which of the following chlorofluorohydrocarbons is chiral:

(a)CF3CH2Cl3; (b) CF2HCHFCCl3; (c) CClFHCHHCCl2F ?

(5)

Q6 :

Do the structures in each of the following pairs represent identical molecules or pairs of enantiomers?

Q7 :

Assign a configuration to each of the following alkens:

(6)

Ch28

Q1 :

Of the following, the one that is not a constituent of a nucleic acid chain is (a) purine base; (b) phosphate group; (c) glycerol; (d) pentose sugar; (e) pyrimidine base.

Q2 :

The structure of the DNA molecule is best described as (a) a random coil; (b) a double helix; (c) a pleated sheet; (d) partly coiled; (e) a branched chain.

Q3 :

Which molecule is not optically active?

(a) 1,2-dichlorobutane; (b)1,4-dichlorobutane; (c) 1,3-dichlorobutane;

(d) 1,2-dichloropropane; (e) none of these.

Q4 :

Which of the following amino acid does not have a chiral carbon?

(a) glycine; (b) alanine; (c) threonine; (d) lysine; (e) none of these.

Q5 :

Enantiomers always (a) have an asymmetric carbon; (b) have different physical properties; (c) change the color of light; (d) rotate polarized; (e) none of these.