If half - life of a substance is 5 years, then the total amount of substance left after 15 years, when initial amount is 64 grams is
Correct answer: D. 8 grams
- A. 16 grams
- B. 32 grams
- C. 2 grams
- D. 8 grams
Explanation
Explanation: The half life of a substance is the time taken by half of the substance to decay. In this case if the half life is 5 years, it means that after 5 years half of the substance will remain, after 10 years a quarter will remain and after 15 years, an eigth will remain. Lets calculate the amount of substance left after 15 years, After 5 years half of the substance remains: 64 grams/2 = 32 grams After another 5 years (total of 10 years), half of the remaining substance remains: 32 grams/2 =16 grams After another 5 years(total of 15 years), half of the remaining substance remains: 16 grams/2 = 8 grams So, after 15 years, when the initial amount was 64 grams, there will be 8 grams of the substance remaining.
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About Reaction Kinetics
Reaction kinetics relates reaction rate to concentration, temperature, surface area and catalysts. Questions cover rate laws, reaction order, rate constants, activation energy and the activated complex, including how a catalyst lowers the activation energy without changing the overall energy change or equilibrium position.
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