(a) Calculate the number of electrons in a small, electrically neutral silver pin that has a mass of 7.0 g. Silver has 47 electrons per atom, and its molar mass is 107.87 g/mol.

The number of electrons in given amount of silver are

Explanation:

The number of moles is defined as the ratio of the mass of a substance to its molar mass.

The equation used is:

......(1)

We are given:

Mass of silver = 7.0 g

Molar mass of silver = 107.87 g/mol

Putting values in equation 1:

According to the mole concept:

1 mole of a compound contains number of particles.

Number of electrons per atom of silver = 47

So, 0.065 moles of silver will contain = number of electrons

Hence, the number of electrons in given amount of silver are

given:

mass of na = 115 g

excess cl2

to determine:

mass of nacl produced

explanation:

given reaction is-

2na(s) + cl2(g) → 2nacl(s)

since cl2 is in excess, na will be the limiting reagent

as per the reaction stoichiometry na: nacl = 1: 1

i.e. moles of na reacted = moles of nacl formed

now, # moles of na = mass of na/atomic mass

                                  = 115 g/23 g.mol-1 = 5 moles

therefore, moles of nacl = 5

molar mass of nacl = 58 g/mol

mass of nacl = 5 moles * 58 g.mol-1 = 290 g

ans: amount of nacl produced = 290 g