Sodium-24 has a half life of 15 hours. Suppose you had a sample containing 0.010 moles of Na-24. How many hours would be required to reduce your sample to 6.25x10^-4 moles

Answer : The time required would be, 60.0 hours

Explanation :

Half-life = 15 hr

First we have to calculate the rate constant, we use the formula :

Now we have to calculate the time passed.

Expression for rate law for first order kinetics is given by:

where,

k = rate constant  =

t = time passed by the sample  = ?

a = initial amount of the reactant  = 0.010 mol

a - x = amount left after decay process = 6.25 × 10⁻⁴ mol

Now put all the given values in above equation, we get

Therefore, the time required would be, 60.0 hours

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a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.