someone help me.

Question

15.4g of methanol (CH3OH 32.042 g/mol) reacts completely according to the following reaction:

CH3OH (g) -----> CH2O(g) + H2(g)

if 12.35 g of formaldehyde (30.026 g/mol) is produced, what is the percent yield for this reaction.

Answer 1

Hello Dontay,

In order to find the percent yield, we need to first calculate the theoretical yield.

To calculate the the theoretical yield, the first step is always to balance the chemical reaction.

Here, the reaction is already in the balanced form:

(1) CH3OH (g) ------> (1) CH2O (g) + (1) H2 (g)

Remember,

The coefficients (in the parentheses) used to balance the reaction indicates the proportionate number of moles of the reactants used and the proportionate number of moles of the product produced ------ Always.

[To brush up, Moles = amount of the substance that weighs equal to the molecular weight of the substance and contains particles (atoms/molecules/ions) equal to the Avogadro's number = 6.022 x 10^23]

In the given chemical reaction, the molar ratio of CH3OH used to the molar ratio of CH2O produced is 1:1.

Meaning, for every single mole of CH3OH reacted, there will be one mole of CH2O produced.

Remember, 1:1 is the molar proportion of the reactant and product. It is not necessary that we always start with 1 mole of CH3OH. What it means is, if we start with say 0.786 moles of CH3OH, we will end up getting 0.786 moles of CH2O. Likewise, if we start with 5.982 moles of CH3OH, we will end up getting 5.982 moles of CH2O and so on.

The next step is to find the actual number of moles of the reactant that reacted.

It is given that 15.4 grams of CH3OH reacted (CH3OH 32.042 g/mol).

Therefore, number of moles reacted = 15.4/32.04 = 0.4812 moles

Since, 1:1 is the molar proportion of the reactant and product, therefore,

0.4812 moles of CH2O (30.026 g/mol) is produced.

If 0.4812 moles of CH2O is produced, therefore,

0.4812 x 30.026 = 14.436 grams of CH2O is produced -----This is the theoretical yield.

The last step is to find the percent yield, which is:

(Actual yield/Theoretical yied) x 100

It is given that 12.35 grams of CH2O was produced, which is the actual yield.

Therefore,

Percent Yield = (12.35/14.436) x 100 = 85.55%

Hope the explanation helps.

Good luck! :)

Answer 2

CH3OH (g) -----> CH2O(g) + H2(g)

From this balanced equation, we see that 1 mole methanol (CH3OH) produces 1 mole formaldehyde (CH2O). So we will find out how many moles methanol we have in 15.4 g, and that will tell us moles formaldehyde produced. Then we just convert that to grams of formaldehyde. This is all done in tge following calculation:

15.4 g CH3OH x 1 mol/32.042 g x 1 mol CH2O/mol CH3OH x 30.026 g/mol = g CH2O = theoretical yield

% yield = actual/theoretical (x100%) 12.35g/theoretical x 100 = answer