Uranium–232 has a half-life of 68.9 years. A sample from 206.7 years ago contains 1.40 g of uranium–232. How much uranium was originally present?

Original amount of uranium is 11.3 g.

Explanation:

Given data:

Half life of uranium = 68.9 years

Time taken in decaying= 206.7 years

Amount left after decaying = 1.40 g

Original amount of uranium = ?

Solution;

Formula:

K = 2.303/t log[A₀]/[A] (1)

A₀ = initial amount

A = amount left after decaying

Value of K from first order kinetics.

Half life of uranium = 0.693 /K

68.9 years = 0.693 /k

k = 0.693/68.9 years

k = 0.0101 year⁻¹

Now we will put the values in formula (1)

K = 2.303/t log[A₀]/[A]

0.0101 year⁻¹ = 2.303/206.7 year log [A₀]/[1.40 g]

[A₀] = 11.3g

Original amount of uranium is 11.3 g.

11.2 is the answer, the guy above just copied it from a guy on another question I think. And they are both wrong. 11.3 is not the answer.

answer is: naturally occurring solid, inorganic compound or element is mineral.

minerals usually have crystalline form, that means than crystal constituents (atoms, molecules or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.

for example magnetite is a mineral of iron oxide (fe₂o₃).

calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (caco₃).

dolomite is an   carbonate mineral composed of calcium magnesium carbonate (camg(co₃)₂).