A freshly prepared sample of radioactive isotope has an activity of 10 mCi. After 4 hours, its activity is 8 mCi. Find: (a) the decay constant  and half-life T1/2; (b) How many atoms of the isotope were contained in the freshly prepared sample? (c) What is the sample's activity 30 hours after it is prepared?

(a). The decay constant is

The half life is 11.3 hr.

(b). The value of N₀ is

(c). The sample's activity is 1.87 mCi.

Explanation:

Given that,

Activity

Time

Activity R= 8 mCi

(a). We need to calculate the decay constant

Using formula of activity

Put the value into the formula

We need to calculate the half life

Using formula of half life

Put the value into the formula

(b). We need to calculate the value of N₀

Using formula of

Put the value into the formula

(c). We need to calculate the sample's activity

Using formula of activity

Put the value intyo the formula

Hence, (a). The decay constant is

The half life is 11.3 hr.

(b). The value of N₀ is

(c). The sample's activity is 1.87 mCi.

freezing

deposition

condensation

explanation;

melting also called fusion is the process where solid becomes liquid, sublimation is the process where solid becomes gaseous without first changing to liquid, deposition involves change from gaseous to solid state, freezing involves change from liquid to solid, boiling or evaporation involves change of liquid to gaseous state, while condensation is the change from gaseous state to liquid state.

endothermic reactions involves absorption of heat from the surroundings or the environment while exothermic reactions involves loss of heat energy to the surroundings.

in this case, sublimation, evaporation and melting are endothermic reactions (gain energy from the environment) while, freezing, deposition and condensation are exothermic (loss of energy to the surroundings) reactions.

their crystal patterns have been disrupted by stress