Chemistry question help

I need help with this chemical reaction question. I got the first part of it right, but I'm completely lost on the other few part:

In a chemical reaction 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 25.8g of substance A reacts? The molar mass of substance A is 29.8 g/mol.

I need to convert the moles of A to B, and then convert the moles of B to molecules.

Hi Sam,


I m french (Boulogne sur mer 62200 - FRANCE)


. . 2A . . . -----> . . . 3B

2 moles . . . . . . . 3 moles


n(A) = m(A) / M(A)
n(A) = 25,8 / 29,8
n(A) = 0,866 mole of A


. . . according the equation :

2 moles of A gives 3 moles of B

. . . then :

0,866 mole of A gives 3 x 0,866 / 2 = 1,299 mole of B



Avogadro's number is : NA = 6,02•10^23 mole^-1


N(B) = NA x n(B) = 6,02•10^23 x 1,299 = 7,818•10^23 molecules of B



I hope to have answer your question.
.