CHEMISTRY HIGH SCHOOL

An original sample of the radioisotope fluorine-21 had a mass of 80.0 milligrams. Only 20.0 milligrams of this original sample remain unchanged after 8.32 seconds. What is the half-life of fluorine-21?(1) 1.04 s (3) 4.16 s
(2) 2.08 s (4) 8.32 s

Answers

Answer 1

Answer:

Answer: The correct answer is Option 3.

Explanation:

All the radioisotope decay processes follow first order kinetics.

Rate law expression for first order kinetics is given by the equation:

$k=(2.303)/(t)\log(a)/(a-x)$

where,

k = rate constant = ?

t = time taken for decay process = 8.32 seconds

a = initial amount of the reactant = 80 mg

a - x = amount left after decay process = 20 mg

Putting values in above equation, we get:

$k=(2.303)/(8.32sec)\log(80g)/(20)\n\nk=0.166sec^(-1)$

The equation used to calculate half life for first order kinetics:

$t_(1/2)=(0.693)/(k)$

where,

$t_(1/2)$ = half life of the reaction = ?

k = $0.166sec^(-1)$

Putting values in above equation, we get:

$t_(1/2)=(0.693)/(0.166sec^(-1))=4.16sec$

Hence, the correct answer is Option 3.

Answer 2

Answer:

4.16s

Explanation:

N = 20*10⁻³g

N₀ = 80*10⁻³g

t = 8.32

N = N₀e⁻λt

In(N/N₀) = -λt

-λ = 1/t * In(N/N₀)

-λ = 1 / 8.32 * In (20*10⁻³ / 80*10⁻³)

-λ = 0.12 * In(0.25)

-λ = -0.167

λ = 0.167

t½ = 0.693 / λ

t½ = 0.693 / 0.167

t½ = 4.16s

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Answers

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the answer is liquid to gas :)

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Answers

Answer:

2) ½N2(g) + O2(g) + 8.1 kcal → NO2(g)

Explanation:

Chemical reactions in general can be classified as endothermic and exothermic reactions.

Endothermic reactions are accompanied by the absorption of energy. Here, the enthalpy (ΔH) change of the reaction is positive.

Exothermic reactions are accompanied by the release of energy. Here, the enthalpy (ΔH) change of the reaction is negative.

1)H2(g) + ½O2(g) → H2O(g), ΔH = -57.82 kcal

Here, ΔH is negative, hence exothermic

2)½N2(g) + O2(g) + 8.1 kcal → NO2(g)

Here, energy is being absorbed, hence endothermic

3) ½N2(g) + 3/2H2(g) → NH3(g) + 11.0 kcal

Here, energy is released, hence exothermic

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Here, ΔH is negative, hence exothermic

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Answers

The part of the nervoussystem is a gray, wrinkled organ consist of millions of neurons is the brain. Therefore, option B is correct.

What is nervous system ?

The nervous system is made up of the brain, spinal cord, and a sophisticated network of nerves. By this system, the body and the brain are transmitted. The brain performs every physical function. The spinal cord moves the brain through the back.

The brain and spinal volume unit are the organs of the central nauseous system. Since they are so vitally important, the brain and spinal cord, which are located in the dorsal body cavity, are protected by a bone shell.

Your entire body is controlled by your brain. Even when you sleep, it controls practically all of your behaviors and runs the show. For something the size of a wrinkled sponge of grey, it was really bad.

Thus, option B is correct.

To learn more about the nervous system, follow the link;

brainly.com/question/29355295

#SPJ6

The answer to your question is b the brain

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Answers

Answer:

Desk

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Cloud

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Explanation:

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