Which of the following four fatty acids has the lowest melting point? 1. сњењењењенгсоон г. сњењењењењењењењењеоон 3. ch3ch2ch2ch2ch2ch2ch2cooh ch3ch-chch2ch2cooh a. 1 b. 2

Option (1) is the correct answer.

Explanation:

Melting point is defined as the point at which a solid state of a substance starts to melt and it converts into liquid state.

Also, it is known that more is the number of linear carbon atoms attached to each other, more is the melting point of a substance. Whereas more is the branching present in a compound least will be its melting point.

For example, has only 5 carbon atoms attached to carboxylic acid group. Whereas has 9 carbon atoms attached to carboxylic acid group.

Therefore, compound will have low melting point.

Thus, we can conclude that out of the given options, fatty acid has the lowest melting point.

part 1: the half-life of the element is 22 years.

part 2: it will take 132.02 year for the sample to decay from 308.0 g to 4.8125 g.

explanation:

part 1: there are two ways to determine the half life time.

first way: the half life time can be determined directly from its definition as it is the time required for the sample to decay to its half concentration.

from the data the initial concentration was 45.0 g and decayed to its half value (22.5 g) in 22.0 years.

second way: the radio active decay is considered first order reaction so we can use the laws of first order reactions.

k = (1/t) ln (a/a-x), where k is the rate constant of the reaction,

t is the time of the reaction

a is the initial concentration of the reactant

a-x is the remaining concentration at time (t)

a = 45.0 g the initial concentration at t = 0 year.

at t = 22 year, a-x = 22.5 g

then k = (1/22 year) ln (45.0 g/ 22.5 g) = 0.0315 year-1.

the half-life time (t1/2) = ln 2/ k = 0.693/ k =0.693/ 0.0315 = 22 years.

part 2:

using the same law k = (1/t) ln (a/a-x),

using the given data; a = 308.0 g and a-x = 4.8125 g and the calculated k from the part 1 (k = 0.0315 year-1)

t = (1/k) ln (a/a-x) = (1/0.0315) ln (308.0/ 4.8125) = 132.02 years