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4 years ago

Which of these represents a chemical change?

Chemistry

2 answers:

Art [367]4 years ago

8 0

Option C. A compound being separated into 2 elements represents a chemical change.

Solnce55 [7]4 years ago

7 0

Answer : The correct option is, (C) a compound being separated into two elements

Explanation :

Chemical change : It is a change where changes occurs in the chemical composition and thus resulting in the formation of new compound or substance. It is an irreversible reaction.

The indication of chemical changes are :

Formation of gas bubbles.

Formation of precipitate.

Change in color.

Change in temperature.

Change in volume.

Change in smell or taste.

Evolution of heat, light and sound.

Physical change : It is a change in which shape and size of a substance changes. In this there is no change in the chemical composition of the substance and no new substance is forming. It is a reversible reaction.

The mixtures are physical combinations.

The indication of chemical changes are :

Change in shape.

Change in form.

Change in size.

Change in phase.

As per question, the option A, B and C is a physical change and option C is a chemical change.

Option C is a chemical change because when a compound being separated into two elements then their chemical compositions are changes and thus resulting in the formation of new compound or substance.

Hence, the option C represents a chemical change.

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Determine the total time that must elapse until only ¼ of an original sample of the radioisotope Rn-222 remains unchanged.

Arte-miy333 [17]

Answer:

7.6 days

Explanation:

Radon is a radioactive element and Radon-222 is it's most stable isotope. The half-life of Radon-222 has been found to be approximately 3.8 days.

Let, the initial amount of the Rn-222 = 1 = A

Final amount = $\frac{1}{4}$ = A'

We will use the following relation for calculating time elapsed in the decay

$A' = A(\frac{1}{2} )^\frac{t}{t_1_/_2} }$

Thus,

$\frac{1}{4} =1(\frac{1}{2} )^\frac{t}{3.8}$

We can write is as,

$(\frac{1}{2} )^2=(\frac{1}{2} )^\frac{t}{3.8}$

Since the base in both sides are equal, powers can also be equal and thus,

$2=\frac{t}{3.8}$

So, t = 7.6 days

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3 years ago

Which property of gases is explained by the process of diffusion?

Sindrei [870]

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3 years ago

Read 2 more answers

PLEASE ANSWER

RoseWind [281]

It is a radio wave

Explanation:

The energy of an electromagnetic waves is related to its frequency by the equation:

$E=hf$

where

h is the Planck constant

f is the frequency of the wave

We notice that the energy of an electromagnetic wave is proportional to its frequency. This means that waves with higher frequencies, such as gamma rays, x-rays, are more energetic, while waves with lower frequencies, such as microwave and radio waves, are the less energetic.

In this case, we want to find the frequency of a wave with energy

E = 0.000001 eV

Converting into Joules,

$E=1\cdot 10^{-6} eV \cdot 1.6\cdot 10^{-19} J/eV=1.6\cdot 10^{-25} J$