Air is about 78% nitrogen gas (N2) by mass. The molar mass of nitrogen gas is 28.0 g/mol. A 100.0-g sample of air contains how many moles of nitrogen?
2.8
3.6
28
78

2.8 moles

Explanation:

Data obtained from the question include:

Percentage composition of N2 in air = 78%

Molar mass of N2 = 28g/mol

Mass of air = 100g

Number of mole of N2 =..?

Next, we shall determine the mass of N2 in air. This can be obtain as follow:

Mass composition of N2 in air = 78% of 100

= 78/100 x 100 = 78g

Therefore, the mass of the N2 in air is 78g

Finally, we shall determine the number of mole of N2 as follow:

Molar mass of N2 = 28g/mol

Mass of N2 = 78g

Number of mole of N2 =.?

Mole = mass /Molar mass

Number of mole of N2 = 78/28

Number of mole of N2 = 2.8 moles.

Therefore, 100g of air contains 2.8 moles of N2

catya that's not even a b or c

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.