How many molecules are in 2.5 mol of NaCl? (a) 1.51×10^24
(b) 146
(c) 1.51×10^23
(d) 4.15

1.51 x 10²⁴molecules

Explanation:

Given parameters:

Number of moles of NaCl  = 2.5moles

Unknown:

Number of molecules  = ?

Solution:

The number of molecules that can be found in a given mole is given as the Avogadro's constant;

       1 mole of substance  = 6.02 x 10²³ molecules

       2.5 mole of NaCl  = 2.5 x 6.02 x 10²³ molecules

                                       = 1.51 x 10²⁴molecules

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.