Question

Assertion: The empirical mass of ethene is half of its molecular mass.
Reason: The empirical formula represents the simplest whole number ratio of various atoms present in a compound.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
C. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect

Answer 1

Hint: The molecular formula of ethene is \[{C_2}{H_4}\] . It is an organic compound made of hydrogen and carbon, these types of compound are known as hydrocarbons. It has a double bond between the carbon-carbon atom. An empirical formula is the simplest ratio of atoms.

Complete step by step answer:
To find out an empirical formula of a compound we need to follow this steps:
Step 1 -write down each element according to the compounds symbol.
Step 2 - write down the number of atoms of that element present in the compound.
Step 3 –now find out the common factor including every element and divide it from each count of elements.
Step 4 –repeat step 3 until you do not get any common factor.
Step 5 – now write down the formula according to the remaining count of atoms
Now, by following the above steps we can find the answer to the questions.
For ethane:
Step 1 -Molecular formula- \[{C_2}{H_4}\]
Step 2 - $C - 2$, $H - 4$
Step 3- the common factor between both element is 2
Hence dividing by 2 we get
$C - 1$ , $H - 2$
Step 4 – there is no more common factor between these two except 1
Therefore, \[C - 1\] , $H - 2$
Step -5 the empirical formula of ethene is
$C{H_2}$
From above observation we can say that both Assertion and Reason are correct and Reason is the correct explanation for Assertion.

So, option A is correct.

Note:
If we have the empirical formula of a compound then we can determine its molecular formula if we are provided with the molecular mass of the compound. Divide the molecular mass of the compound with empirical mass of the compound, you will get a whole number. Multiply that whole number with the subscript of empirical formula and you will get its molecular formula.