Niobium-91 has a half-life of 680 years. after 2,040 years, how much niobium-91 will remain from a 300.0-g sample?
3 g
18.75 g
37.5 g
100.0 g

37.5 g

Explanation:

Radioactive decay follows first order kinetics.

Thus Half-life of sample of Niobium-91 = 680 years

N= amount left after time t

= initial amount

t= time of decay

= 300 g, t= 2040 years,

N=37.5g

if the concentration of products is decreased, the equilibrium will shift toward the products). add an inert gas (one that is not involved in the reaction) to the constant-volume reaction mixture: this will increase the total pressure of the system, but will have no effect on the equilibrium condition.

explanation:

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).