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4 years ago

What is potassium 39.098

1 answer:

3 0

Group1 Melting point63.5°C, 146.3°F, 336.7 K Period4 Boiling point759°C, 1398°F, 1032 K Blocks Density (g cm−3)0.89 Atomic number19 Relative atomic mass39.098 State at 20°CSolid Key isotopes39K

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The half-life of a certain radioactive substance is 12 hours. There are 19 grams present initially. a. Express the amount of su

neonofarm [45]

Answer:

(a) $N=19\times e^{-\lambda t}$

(b) 15 hours

Explanation:

half life, T = 12 hours

No = 19 g

(a) Let N be the amount remaining after time t.

Let λ be the decay constant.

$\lambda =\frac {0.6931}{T}$

The equation of radioactivity used here is given by

$N=N_{o}e^{-\lambda t}$

$N=19\times e^{-\lambda t}$

(b) N = 8 gram

Substitute the values in above equation

$\lambda =\frac {0.6931}{12}$

λ = 0.0577 per hour

So, $8=19\times e^{-0.577t}$

$e^{-0.0577t}=0.421$

Take natural log on both the sides

- 0.0577 t = - 0.865

t = 15 hours

4 0

3 years ago

Scientists discovered that the level of deuterium in comets forming in the Kuiper Belt is nearly identical to the level found in

malfutka [58]

Options:

The impact of Earth’s gravity on the decay rate of deuterium is the same as the impact of microgravity.
Most of the water that forms the oceans of Earth arrived by way of impacts with Kuiper Belt comets.
Most comets formed from deuterium-based water that was stripped away from early Earth by solar radiation.

Answer:

Most of the water that forms the oceans of Earth arrived by way of impacts with Kuiper Belt comets.

Explanation:

Note, a comet is a celestial body made of ice which releases gases when it orbits close to the Sun. Deuterium is a type of element which can be found in comets and in our oceans on earth. Deuterium is considered an isotope of hydrogen.

Hence, because of the similarities between the Deuterium and Hydrogen, some scientists promote the theory that most of the water that forms on oceans of the earth likely arrived by the impact with Kuiper Belt comets.

3 0

3 years ago

You have a radioactive sample with a half-life of 1 hour. At t = 1 hour, a Geiger counter measures its radiation at 40 counts/mi

Mama L [17]

Answer:

Explanation:

Given that, .

The half-life of a radioactive element is

t½ = 1 hr.

At the first hour, the radioactive element has 40 counts/minute

After 4 hours it has 5 counts/minute

So,

We want to filled the table.

0 hours, I.e at the start

40 counts/mins × 2 = 80 counts / mis

First half-life (first hour) is

40 counts/mins

Second half-life (second hour)

40 counts/mins × ½ = 20 counts/mins

Third half-life (third hour)

40 counts/mins × ¼ = 10 counts / mins

Fourth half life (fourth hour)

40 counts/mins × ⅛ = 5 counts / mins

So, the table is

Time........................Geiger Counter Rate

0 hours.................... 80 counts / minutes

1 hour........................ 40 counts / minutes

2 hours..................... 20 counts / minutes

3 hours..................... 10counts / minutes

4 hours...................... 5 counts / minute

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3 years ago

Andy has two strong magnetic marbles of equal size. What will happen when he puts the two marbles about 2 centimeters apart?

VikaD [51]

I believe it would be C

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4 years ago

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I’ll give brainliest!! please help and answer correctly! plsss answer quick

noname [10]

Answer:

i dont think anything will happen so maybe A: the wall is larger than you.

Explanation:

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3 years ago