Calculate Percent Yield Questions: NaNO3 in Impure Substance (URGENT)

In summary, the question involves calculating the percentage yield of NaNO3 in an impure substance given the amount of NH3 produced from a reaction, which is then used to determine the amount of H2SO4 and NaOH used. The solution involves calculating the amount of H2SO4 reacted with NaOH and NH3, and then using that to calculate the amount of NaNO3 reacted. However, the calculation of the amount of NaNO3 reacted is incorrect, leading to a percentage yield of over 100%, which can indicate an error in the impurity or a mistake in the calculation.
  • #1
Originaltitle
16
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% yield questions (URGENT)

Homework Statement


We have 3 equations:
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1.64 g of an impure NaNO3-containing substance is reacted with Devarda's alloy. The amount of NH3 got from this reaction is reacted with 25cm3 1.00 moldm-3 H2SO4. The H2SO4 left over is reacted with 16.2 cm3 2.00 moldm-3 NaOH. Calculate the percentage yield of NaNO3 in the impure substance.2. The attempt at a solution

My attempt at an answer:
1. Amount of H2SO4 reacted with NaOH = (2.00 x 16.2 x 10-3) / 2 = 0.0162 moles.
2. Amount of H2SO4 reacted with NH3 = 0.025 - 0.0162 = 0.0088 moles.
3. Amount of NH3 reacted = (0.0088 x 2) = 0.0176 moles.
4. Amount of NaNO3 reacted = 0.0176 x (3/2) = 0.0264.
5. Mass of NaNO3 reacted = 0.0264 x 85 = 2.244 g.

% yield = 2.244/1.64 = 137 %.

It's wrong because the final mass can't be more than the initial. HELP!
 
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  • #2
Originaltitle said:
4. Amount of NaNO3 reacted = 0.0176 x (3/2) = 0.0264.

Why 3/2?

It's wrong because the final mass can't be more than the initial. HELP!

% yields over 100% do happen. They usually mean something is wrong, but it is not necessarily a math error. For example in this case it could mean that the impurity is some other nitrate.
 
  • #3
The error is in the line:
Originaltitle said:
4. Amount of NaNO3 reacted = 0.0176 x (3/2) = 0.0264.
 
  • #4
Edit: But Borek already told you that...
 
  • #5


I would like to point out that there are a few issues with the approach taken in the solution provided. Firstly, it is important to note that the given information is not sufficient to determine the percentage yield of NaNO3 in the impure substance. In order to calculate the percentage yield, we would need to know the actual amount of NaNO3 present in the impure substance before the reaction.

Secondly, the equations used in the solution are not balanced. For example, in step 4, the amount of NaNO3 reacted is calculated by multiplying the amount of NH3 reacted by a factor of 3/2. However, this is incorrect as the balanced equation for the reaction between NH3 and H2SO4 is:

2NH3 + H2SO4 → (NH4)2SO4

This means that for every 2 moles of NH3 reacted, only 1 mole of H2SO4 is consumed. Therefore, the correct calculation would be:

Amount of NaNO3 reacted = 0.0176 x (1/2) = 0.0088 moles.

Thirdly, the mass of NaNO3 reacted is calculated by multiplying the amount of NaNO3 by its molar mass of 85 g/mol. However, this is not accurate as the given information does not specify the purity of the NaNO3-containing substance. Therefore, it is not appropriate to assume that all of the mass obtained in the final product is solely due to NaNO3.

In conclusion, it is important to carefully analyze the given information and ensure that all equations are correctly balanced before attempting to calculate the percentage yield. Additionally, the purity of the reactants and products should also be taken into consideration in order to obtain an accurate result.
 

Related to Calculate Percent Yield Questions: NaNO3 in Impure Substance (URGENT)

1. What is percent yield and how is it calculated?

Percent yield is a measure of the efficiency of a chemical reaction. It represents the percentage of the theoretical yield (the amount of product that should be produced based on the starting materials) that is actually obtained in the reaction. It is calculated by dividing the actual yield (the amount of product obtained in the reaction) by the theoretical yield and multiplying by 100.

2. Why is the percent yield of a reaction important?

The percent yield of a reaction is important because it provides information about the efficiency and quality of the reaction. A high percent yield indicates that the reaction is efficient and that most of the starting materials were converted into the desired product. On the other hand, a low percent yield can indicate issues with the reaction, such as incomplete conversion of starting materials or side reactions occurring.

3. How does the percent yield of a reaction affect the overall cost of production?

The percent yield of a reaction can greatly impact the overall cost of production. A high percent yield means that a larger amount of product is obtained from a given amount of starting materials, leading to lower production costs. On the other hand, a low percent yield means that more starting materials will be needed to obtain the desired amount of product, resulting in higher production costs.

4. What factors can affect the percent yield of a reaction?

There are several factors that can affect the percent yield of a reaction, including the purity of the starting materials, the efficiency of the reaction conditions, and the presence of side reactions or impurities. Other factors, such as temperature, pressure, and concentration, can also have an impact on the percent yield.

5. How can the percent yield of a reaction be improved?

There are a few ways to improve the percent yield of a reaction. These include using high-quality and pure starting materials, optimizing reaction conditions, and carefully monitoring and controlling any potential side reactions. Additionally, using catalysts or adjusting reaction parameters, such as temperature and concentration, can also improve the percent yield of a reaction.

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