As with any combustion reaction, the products of combusting a hydrocarbon fuel (cxhy) with oxygen (o2) are carbon dioxide (co2) and water (h2o).

a mass of 15.51 g for an unknown fuel was combusted in a reaction vessel containing an unknown amount of oxygen. at the end of the reaction, there still remained 15.46 g of the fuel as well as 0.0817 g of water and 0.1497 g of carbon dioxide. the oxygen was completely consumed during the reaction.

how many molecules of oxygen gas were initially present in the reaction vessel?

The number of oxygen gas molecules initially present are

Explanation:

The balanced chemical reaction for the combustion of given hydrocarbon follows:

To calculate the number of moles, we use the equation:

For carbon dioxide:

Given mass of carbon dioxide = 0.1497 g

Molar mass of carbon dioxide = 44 g/mol

Putting values in above equation, we get:

Thus,

For water:

Given mass of water = 0.0817 g

Molar mass of water = 18 g/mol

Putting values in above equation, we get:

Thus,

To calculate the number of moles of oxygen, we solve the equation for its coefficient by putting values of 'x' and 'y', we get:

According to mole concept:

1 mole of a compound contains number of molecules.

So, moles of oxygen will contain = molecules.

Hence, the number of oxygen gas molecules initially present are

U whay do you need with?

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.