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3 years ago

Which situation is an indication that a chemical change has occurred?

Chemistry

2 answers:

andreev551 [17]3 years ago

4 0

Heat is released.

When a chemical change occurs, energy comes out of the atoms which causes heat.

coldgirl [10]3 years ago

3 0

Answer: Option (A) is the correct answer.

Explanation:

Chemical changes are defined as the change which tend to show difference in chemical composition of a substance.

For example, toxicity, reactivity, combustion etc are all chemical properties.

So, in the given situation formation of bubbles shows that a gas has been formed which is a chemical change.

A chemical change will always lead to the formation of a new compound and this change is irreversible in nature by any physical means.

On the other hand, a change which is unable to bring any difference in chemical composition of a substance is known as a physical change.

For example, change in shape, size, mass, volume etc are all physical properties.

Thus, we can conclude that a gas is formed is an indication that a chemical change has occurred.

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one part of dalton's atomic theory states: compounds are formed by combinations of atoms from two or more elements. is this stat

ANEK [815]

Answer:

The statement is considered to be true

Explanation:

The statement is true because when elements chemically combine, there are interactions between their valence electrons, causing the two elements to be bonded together to form what is known as a compound.

Compounds can only be formed from interactions between two or more elements. examples include:

Hydrogen + Oxygen = H2O (water)

Sodium + Chlorine = NaCl

Note that if atoms of the same element combine, what is formed is a molecule, not a compound. Some atoms usually do this to attain stability. examples include = O2 H2 and N2. They are oxygen molecule, hydrogen molecule, and nitrogen molecule respectively.

Compounds are only formed when different elements combine to attain electronic stability.

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3 years ago

Rounded to the nearest whole number, how many neutrons, on average, are in an atom of osmium? 76 114 190 266

Sonja [21]

Osmium has 114 neutrons on average

5 0

4 years ago

Read 2 more answers

What would be the major product obtained from hydroboration–oxidation of the following alkenes?

zmey [24]

Answer:

a. 3-methylbutan-2-ol

b. 2-methylcyclohexan-1-ol

Explanation:

For this reaction, we must remember that the hydroboration is an "anti-Markovnikov" reaction. This means that the "OH" will be added at the least substituted carbon of the double bond.

In the case of 2-methyl-2-butene, the double bond is between carbons 2 and 3. Carbon 2 has two bonds with two methyls and carbon 3 is attached to 1 carbon. Therefore the "OH" will be added to carbon three producing 3-methylbutan-2-ol.

For 1-methylcyclohexene, the double bond is between carbons 1 and 2. Carbon 1 is attached to two carbons (carbons 6 and 7) and carbon 2 is attached to one carbon (carbon 3). Therefore the "OH" will be added to carbon 2 producing 2-methylcyclohexan-1-ol.

See figure 1

I hope it helps!

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3 years ago

Which of the following statements is true when considering temperature during a recrystallization? More than one answer may be c

Otrada [13]

Answer:

The correct answer is:

(1) It is important that the sample is dissolved in just enough hot solvent.

Explanation:

The process of recrystallization is important to eliminate the impurities and to obtain better crystals of the solid. The solvent used to perform the recrystallization must have a high dissolution power of the substance to be recrystallized and a low dissolution power of the impurities. This is in order to eliminate most impurities. Furthermore, It is important that the sample is dissolved in just enough hot solvent because this should be easy to remove after the recrystallization and the crystal should form easily when the solution cools. Also, it is better to add the hot solvent to solubilize the crystals and keep the impurities insoluble, instead of adding the cold solvent and heating the solution. Additionally, the process of cooling the solution must be done slowly to obtain large and fewer crystals. A fast ice-cooling will form smaller crystals.

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3 years ago

The following diagram shows various positions of the moon in its orbit around Earth. The image of the moon shows its phase as se

Serga [27]

Answer:

Position D

Explanation:

One fourth of the Moon will be visible from Earth when the Moon is in position D. The reason why this is the right position is that the Moon will be in a position where the majority of its surface that is lighted by the Sun is facing the Sun. On the other hand, the angle is just right that about one quarter of the lighted part of the Moon is also facing the Earth. This will result in a perception from the Earth's view point that the Moon is lighted at one quarter of its surface.

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4 years ago