Answer:

Explanation:
Hello there!
In this case, according to the given information, it turns out possible for us to find the molecular formula of the given compound by firstly calculating both moles and grams of carbon in carbon dioxide and hydrogen in water, as the only sources of these elements derived from the compound x due to its combustion:


Now, since the addition of carbon and hydrogen is about 6.50 grams, we infer the compound has no oxygen, that is why we now set the mole ratios in the empirical formula for both C and H as shown below:

Yet it cannot be decimal, that is why we multiply by 4 to get the correct whole-numbered empirical formula:

Whose molar mass is 64.09 g/mol, which makes the ratio of molar masses:

Therefore, the molecular formula is twice the empirical one:

Regards!
Here, Molar mass of N2O4 = 92.02 g/mol
So, Number of molecules in 1 mole (92.02 g) = 6.023 * 10²³
Number of molecules in 76.3 g = 6.023 * 10²³ / 92.02 * 76.3
= 6.023 * 10²³ / 1.20
= 5 * 10²³
In short, Your Answer would be approx. 5 * 10²³ molecules
Hope this helps!
Answer:
the molecular formula of paradichlorobenzene is C6H4CL2
Answer : The structure are shown below and the number of stereoisomers are possible in 3,5-dimethylnonane and 3,7-dimethyle-5-ethyldecane are 4 and 8 respectively.
Explanation :
Chiral carbon : It is carbon which is attached to the different types of atoms or molecules.
The number of stereoisomers possible for a compound is related to the number of chiral centers (n) present in it as,

where,
'n' is the number of chiral carbon present in the compound.
The number of chiral carbon present in 3,5-dimethylnonane is, 2 that means n = 2 (carbon-3 and carbon-5)

The number of stereoisomers are possible in 3,5-dimethylnonane is, 4
The number of chiral carbon present in 3,7-dimethyle-5-ethyldecane is, 3 that means n = 3 (carbon-3, carbon-5 and carbon-7)

The number of stereoisomers are possible in 3,7-dimethyle-5-ethyldecane is, 8