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abruzzese [7]
3 years ago
12

The half-life of potassium-40 is 1.3 billion years. If a rock that formed 2.6 billion years ago originally contained 5 grams of

potassium-40, about ____ grams of potassium-40 would be left in that rock today
Chemistry
1 answer:
pochemuha3 years ago
8 0

Answer: 1.25 grams of Potassium-40

Explanation: When the amount of a compound is consumed by half, the time passed is called "the half life". This term is particularly important in nuclear chemistry. Potassium-40 is an isotope of potassium element and it is radioactive. As a result, the consumption time of this radioactive isotope is valuable information since radioactive isotopes are detrimental to health and nature.

For example, in this question, within 1.3 billion years, half amount of the potassium-40 disappears. 2.6 billion years ago, there were 5 grams of potassium-40 and when 1.3 billion years pass, half of the 5 grams of potassium-40 will disappear and there will will be 2.5 grams of potassium-40 left (5 grams of potassium-5 grams of potassium*(1/2)[half amount]=2.5 grams of potassium-40 left). As a result, 2.5 grams of potassium-40 is the amount that is present 1.3 billion years ago (2.6 billion years-1.3 billion years [half-life]=1.3 billion years). There will be 1.3 billion years left until today, so we still have to calculate the amount disappeared in 1.3 billion years. Thus, half of the 2.5 grams must disappear in 1.3 billion years left (2.5 grams - 2.5 grams*(1/2)[half amount]=1.25 grams). Finally, we have 1.25 grams of potassium-40 left since 2.6 billion years ago.

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6605.3900 g/

Explanation:

3 0
3 years ago
If the a of a monoprotic weak acid is 2. 6×10−6, what is the ph of a 0. 33 m solution of this acid?
yawa3891 [41]

The pH of the monoprotic weak acid is 2.79.

<h3>What are weak acids?</h3>

The weak acids are the acids that do not fully dissociate into ions in the solution. Strong acids fully dissociate into ions.

The chemical reaction is HA(aq) ⇄ A⁻(aq) + H⁺(aq).

c (monoprotic acid) = 0.33 M.

Ka = 1.2·10⁻⁶

[A⁻] = [H⁺] = x

[HA] = 0.33 M - x

Ka = [A⁻]·[H⁺] / [HA]

2. 6 × 10⁻⁶ = x² / (0.33 M - x)

Solve quadratic equation: [H⁺] = 0.000524 M.

pH = -log[H⁺]

pH = -log(0.000524 M)

pH = 2.79

Thus,  the pH of the monoprotic weak acid is 2.79

To learn more about weak acids, refer to the below link:

brainly.com/question/13032224

#SPJ4

5 0
2 years ago
Cuando se quema 1 mol de metano –o sea, 16 g–, se desprenden 802
Anvisha [2.4K]

Answer:

1 gramo de metano aporta 50.125 kilojoules.

1 gramo de metano aporta 48.246 kilojoules.

Explanation:

La cantidad de energía liberada por la combustión de una unidad de masa del hidrocarburo (Q), en kilojoules por mol, es igual a la cantidad de energía liberada por mol de compuesto (\bar {Q}), en kilojoules por mol, dividido por su masa molar (M), en gramos por mol:

Q = \frac{\bar Q}{M} (1)

A continuación, analizamos cada caso:

Metano

Q = \frac{802\,\frac{kJ}{mol} }{16\,\frac{g}{mol} }

Q = 50.125\,\frac{kJ}{g}

1 gramo de metano aporta 50.125 kilojoules.

Octano

Q = \frac{5500\,\frac{kJ}{mol} }{114\,\frac{g}{mol} }

Q = 48.246\,\frac{kJ}{mol}

1 gramo de metano aporta 48.246 kilojoules.

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3 years ago
Suppose that the C=O group in a peptide bond can be regarded as isolated from the rest of the molecule. Given that the force con
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Answer:

a) v = 1497.2 cm^-1

b) v = 1465 cm^-1

Explanation:

In the attached image is the procedure explained to reach the answer.

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4 years ago
Which statements describe elements?
monitta

Answer: B,C,D

Explanation: Who ever reads this have a great day and stay safe :}

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3 years ago
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