Asample contains 2.2 g of the radioisotope niobium-91 and 15.4 g of its daughter isotope, zirconium-91. how many half-lives have passed since the sample originally formed?

3

Explanation: This is a radioactive decay and all the radioactive process follows first order kinetics.

Equation for the reaction of decay of radioisotope follows:

By the stoichiometry of above reaction,

1 mole of is produced by 1 mole

So, 0.17 moles of will be produced by =

Amount of

decomposed will be = 0.17 moles

Initial amount of  will be = Amount decomposed + Amount left = (0.17 + 0.024)moles =0.194 moles

where,

a = amount of reactant left after n-half lives = 0.024

= Initial amount of the reactant = 0.194

n = number of half lives= ?

Putting values in above equation, we get:

Therefore, 3 half lives have passed.

може ли да зареждате повече информация, моля

(newtons first law)

conservation of momentum law states :

momentum before collision = momentum after collision

momentum p (kg-m/s)= mass * velocity

say moving car=1 000 kg, velocity = 10 m/s then p = 1 000*10= 10 000 kg-m/s

say still car = 2 000 kg, velocity = 0 m/s then p = 2 000* 0 = 0 kg-m/s

total momentum prior to collision = 10 000 + 0 = 10 000 kg-m/s

momentum after collision = 10 000 kg-m/s

mass now = 1 000 kg+2 000 kg = 3 000 kg

10 000 = 3 000 kg* velocity m/s

10 000/3 000 = velocity

3.33 m/s = velocity after collision

an impulse is a force applied over time , momentum is exclusive of external forces and a perfect collision is implied