23. A certain sample of nitrogen gas consists of 9.26 1022 nitrogen atoms. (a) How many moles of N atoms are present in this sample ?
(b) If the gas is entirely in molecular form, how many molecules are present in this
sample?
(c) What is the mass of the sample in gramme?

a) 0.154 moles of N2

b) 9.27 × 10^22 molecules

c) 4.312 g

Explanation:

a)

1 mole of N2 contains 6.02 × 10^23 atoms

x moles of N2 contains 9.26 × 10^22 atoms

x= 9.26 ×10^22/6.02 × 10^23

x= 1.54 ×10^-1

x= 0.154 moles of N2

b)

1 mole of N2 contains 6.02 × 10^23 molecules

0.154 moles of N2 contains 0.154 moles × 6.02 × 10^23 = 9.27 × 10^22 molecules

c)

Molar mass of the nitrogen gas= 28 gmol^-1

Number of moles of nitrogen gas = 0.154 moles

Number of moles = mass/molar mass

0.154 moles= mass/28 gmol^-1

Mass= 0.154 moles × 28gmol^-1

Mass= 4.312 g

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."