Question

In a chemical reaction, exactly 2 mol of substance A react to produce exactly 3 mol of substance B.

2A = 3B

How many molecules of substance B are produced when 28.2 g of substance A reacts? The molar mass of substance A is 17.9 g/mol.

Step 1. Convert the mass of A to moles.

__________________________________mol A

Step 2. Convert the number of moles of A to the number of moles of B.

___________________________________mol B

Step 3. Convert the number of moles of B to molecules of B.

___________________________________molecules of B.

Answer 1

2A 3B

Given molar mass of A is 17.9 g mol^-1

mass of A is 28.2 g

So Number of moles ,

                             

                             n = 1.575 mol

According to the equation , 2 moles of A produces 3 moles of B

                                    1.575 moles of A produces Z moles of B

                                     

                                      Z = 2.36 moles of B

We know that 1 mole of any sustance contains avagadro number of molecules

So 1 mole of B contains 6.023 x 10 23 molecules

    2.36 moles of B contains Y molecules

Y = 14.2 x 10 ²³ molecules of B