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 27.9 g of substance A reacts? the molar mass of substance A is 24.7 g/mol
STEP 1: convert the mass of A to moles
this is what i did :
2mol x 27.9g/24.7g = 2.259109 mol
is it right?
STEP 2 :convert the number of moles of A to the number of moles of B
STEP 3: convert the number of moles of B to molecules of B
Step 1:
You shouldn't multiply by the 2 yet. You will use that in the next step of the problem.
Step 2: Here you will take the moles you got and use the given moles of substance.
1.1296 molA * (3 molB/2 molA)
That will give you the correct number of moles B.
Step 3: Here you use Avogadro's # to find molecules of B.
NOTE: I am not a tutor but I have done problems like this before.
STEP 1: Convert the mass of A to moles
To convert the mass of substance A (27.9 g) to moles, divide the mass by the molar mass:
27.9 g / 24.7 g/mol = 1.129 moles of substance A
So, you made a small calculation error. The correct conversion should be 1.129 moles of substance A.
STEP 2: Convert the number of moles of A to the number of moles of B
According to the balanced chemical equation, 2 moles of substance A react to produce 3 moles of substance B. So:
1.129 moles of A * (3 moles of B / 2 moles of A) = 1.6935 moles of B
STEP 3: Convert the number of moles of B to molecules of B
To convert moles of substance B to molecules, use Avogadro's number, which is 6.022 x 10^23 molecules/mol:
1.6935 moles of B * (6.022 x 10^23 molecules/mol) = 1.019 x 10^24 molecules of B
Therefore, when 27.9 g of substance A reacts, approximately 1.019 x 10^24 molecules of substance B are produced.
Your conversion in Step 1 is correct. To convert the mass of substance A to moles, you used the formula:
moles of A = mass of A / molar mass of A
Substituting the given values:
moles of A = 27.9 g / 24.7 g/mol = 1.128 mol
Now, let's move on to Step 2, which is converting the moles of A to moles of B. From the balanced chemical equation:
2 mol of A produce 3 mol of B
Therefore, the conversion factor is:
moles of A : moles of B = 2 : 3
Using this ratio, we can find the moles of B:
moles of B = (1.128 mol of A) x (3 mol of B / 2 mol of A) = 1.692 mol of B
Finally, in Step 3, you can convert the moles of B to molecules of B. The conversion factor you need is:
1 mol of B = 6.022 x 10^23 molecules of B (Avogadro's number)
Using this conversion factor:
molecules of B = 1.692 mol of B x (6.022 x 10^23 molecules of B / 1 mol of B) = 1.018 x 10^24 molecules of B
So, when 27.9 g of substance A reacts, approximately 1.018 x 10^24 molecules of substance B are produced.