Answer: 17) d. 
18. c. The empirical formula of a compound can be twice the molecular formula.
Explanation:
Molecular formula is the chemical formula which depicts the actual number of atoms of each element present in the compound.
Empirical formula is the simplest chemical formula which depicts the whole number of atoms of each element present in the compound.
To calculate the molecular formula, we need to find the valency which is multiplied by each element to get the molecular formula.
The equation used to calculate the valency is:
The empirical mass can be calculated from empirical formula and molar mass must be known.
17. Thus the empirical formula of should be 
18. The molecular formula will either be same as empirical formula or is a whole number multiple of empirical formula. Thus the empirical formula of a compound can never be twice the molecular formula.
The rows in the top third - This group consists of elements like Sodium, Magnesium, Potassium and Calcium on the right and Chlorine, Carbon, Nitrogen and Oxygen on the left.
Sodium and Chlorine are components of salt, a very important compound of our blood, essential for transferring electrical signals from the brain to the rest of the body and vice versa. Calcium is the building block of our bones, while Magnesium and potassium ensure proper functioning of our organs.
<u>Answer: </u>The molar mass of solute is 115 g/mol.
<u>Explanation:</u>
Elevation in the boiling point is defined as the difference between the boiling point of the solution and the boiling point of the pure solvent.
The expression for the calculation of elevation in boiling point is:
OR
......(1)
where,
Boiling point of pure solvent (benzene) = 
Boiling point of solution = 
i = Vant Hoff factor = 1 (for non-electrolytes)
= Boiling point elevation constant = 
= Given mass of solute = 10 g
= Molar mass of solute = ? g/mol
= Mass of solvent = 200 g
Putting values in equation 1, we get:
Hence, the molar mass of solute is 115 g/mol.
