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3 years ago

10

A radioactive isotope of potassium (K) has a half-life of 20 minutes. If a 40.0 gram sample of this isotope is allowed to decay

for 80 minutes, how many grams of the radioactive isotope will remain?

2 answers:

anzhelika [568]3 years ago

8 0

Answer:

A

Explanation:

A

Ivahew [28]3 years ago

5 0

Answer: 2.5 grams

Explanation:

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Naturally occurring element X exists in three isotopic forms: X-28 (27.979 amu, 92.21% abundance), X-29 (28.976 amu 4.70% abunda

bezimeni [28]

<u>Answer:</u> The average atomic mass of X is 28.09 amu

<u>Explanation:</u>

Average atomic mass of an element is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

$\text{Average atomic mass }=\sum_{i=1}^n\text{(Atomic mass of an isotopes)}_i\times \text{(Fractional abundance})_i$ .....(1)

<u>For isotope 1:</u>

Mass of isotope 1 = 27.979 amu

Percentage abundance of isotope 1 = 92.21 %

Fractional abundance of isotope 1 = 0.9212

<u>For isotope 2:</u>

Mass of isotope 2 = 28.976 amu

Percentage abundance of isotope 2 = 4.70 %

Fractional abundance of isotope 2 = 0.0470

<u>For isotope 3:</u>

Mass of isotope 3 = 29.974 amu

Percentage abundance of isotope 3 = 3.09 %

Fractional abundance of isotope 3 = 0.0309

Putting values in equation 1, we get:

$\text{Average atomic mass of X}=[(27.979\times 0.9212)+(28.976\times 0.0470)+(29.974\times 0.0309)]$

$\text{Average atomic mass of X}=28.09amu$

Hence, the average atomic mass of X is 28.09 amu

4 0

3 years ago

Some forms of vitamin D, C₂₈H₄₄O, can be found in red meat. How many total atoms are in 5 molecules of C₂₈H₄₄O

MaRussiya [10]

Answer:

3.01 × 10^24 atoms of vitamin D

Explanation:

The number of atoms, molecules or ions present in a substance is given by the Avogadro's number which is 6.02 × 10^23.

Hence;

1 molecule of vitamin D contains 6.02 ×10^23 atoms

5 molecules of vitamin D contains 5 × 6.02 ×10^23/1

= 3.01 × 10^24 atoms of vitamin D

7 0

3 years ago

vlada-n [284]

Answer:

El cocodrilo se arrastró durante 20.833 segundos.

Explanation:

El enunciado presenta omisiones y errores conceptuales. La forma correcta es la siguiente: <em>"Un cocodrilo se arrastró 25 metros hacia la derecha con una rapidez promedio de 1.2 metros por segundo. ¿Cuántos segundos se arrastró el cocodrilo?"</em>

Consideremos que el cocodrilo tiene un movimiento rectilíneo uniforme, el tiempo requerido para el recorrido se calcula con la siguiente ecuación cinemática:

$t = \frac{x}{v}$ (1)

Donde:

$x$ - Distancia recorrida, en metros.

$v$ - Rapidez del cocodrilo, en metros por segundo.

$t$ - Tiempo, en segundos.

Si $x = 25\,m$ y $v = 1.2\,\frac{m}{s}$ , entonces el tiempo empleado por el cocodrilo es:

$t = \frac{25\,m}{1.2\,\frac{m}{s} }$

$t = 20.833\,s$

El cocodrilo se arrastró durante 20.833 segundos.

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8 0

3 years ago

Draw the molecules listed below and circle any functional groups present. Provide the following information for each molecule:Mo

aksik [14]

The question requires us to draw the structural formula, provide the name and highlight any functional groups for the compound: diethyl ether.

The molecule diethyl ether can be represented as it follows, with two ethyl groups (-CH2CH3) bonded to a oxygen atom:

Note that the functional group ether (R-O-R) is present in the structre and highlighted in blue in the image. The official name of diethyl ether is ethoxyethane.

3 0

1 year ago

Which example best demonstrates Charles’s law?

Liono4ka [1.6K]

Answer:

A

Explanation:

The Charles law states that the volume of an ideal gas increases when temperature is increased under constant pressure. The pressure inside the balloon is always equal to the atmospheric pressure. Therefore answer A demonstrate the Charles law.

6 0

3 years ago

Read 2 more answers