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.
There are a lot of ways to increase the solubility of the solute. <span>Increasing the temperature, mixing time and surface area of a solvent increases the solubility of the solute</span>
Answer:
to identify the element by using flame tests
Answer:
The wavelength of sunlight is required to break the bond in one oxygen molecule is 242 nm.
Explanation:
Energy required to break the 1 mol oxygen-oxygen bond:
=495 kJ=495000J
1 mol =
molecules
Energy required to break 1 molecule of oxygen molecule= E
= 
The energy required to break the 1 molecule of oxygen is equal to enrgy of one photon of a sunlight.

where,
= wavelength of the light
E = energy of the photon
h = Planck's constant = 
c = speed of light = 


The wavelength of sunlight is required to break the bond in one oxygen molecule is 242 nm.