What is one example of an everyday molecule?

Hydrogen

Explanation:

Just to provide some background, an element is a pure substance consisting of only one type of atom. An atom is the smallest constituent of matter. All elements are comprised of a single type of atom (e.g., gold is composed of gold atoms, helium of helium atoms, phosphorus phosphorus, and so on).

A molecule is a group of two or more atoms. They can be the same atom (homonuclear), such as or different atoms (heteronuclear).

Some examples of homonuclear molecules include:

Hydrogen  (H2)  

Nitrogen  (N2)  

Phosphorus  (P4)  

Some examples of heteronuclear molecules include:

Carbon dioxide  (CO2)  

Sulfuric acid  (H2SO4)  

Methane  (CH4)

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