Chemistry, 16.10.2020 15:01 babytony1210

Which of the following is a CORRECT statement? Chemical change cannot be undone or reversed.

Physical change often cannot be undone or reversed.

In chemical change, you end up with the same substance you started with.

In physical change, particles of 2 or more substances rearrange to form new or different substance.

Answers: 2

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Answer from: ritahastie7533

Detail is given below.

Explanation:

1) Chemical change cannot be undone or reversed.

The given statement is correct. Because,

Chemical change:

The changes, that occur due to change in the composition of a substance and result in a different compound is known as chemical change.

These changes are irreversible .

Example:

Combustion of fuel or wood: that oil or wood convert into energy, CO2 and ash in case of wood and this reaction can not be reversed.

2) Physical change often cannot be undone or reversed.

The given statement is incorrect.

Physical Change

The changes that occur only due to change in shape or physical properties but their chemical or internal composition remain unchanged.

These changes were reversible.

Example :

Water converting to Ice

Water converting to gas

3) In chemical change, you end up with the same substance you started with

The given statement is incorrect. Consider the following example.

The reaction of Hydrogen and oxygen:

H₂ (g) + O₂ (g) > 2H₂O (l)

A totally new compound is formed when oxygen and hydrogen are undergo reaction which is water.

4) In physical change, particles of 2 or more substances rearrange to form new or different substance.

The given statement is incorrect.

When particles rearrange them selves the different substance is not formed. Consider the example of water when it converted into ice or vapors. Only phase is changed but water retain its properties so new substance is not formed.

Answer from: Quest

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1

0.44 / 0.09 = 4.8

mgco3-5h2o"

Answer from: Quest

Noble gases is far right

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Which of the following is a CORRECT statement? Chemical change cannot be undone or reversed.
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