Finding the mass of an aldehyde

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  • Thread starter lioric
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In summary, the conversation discusses the process of hydrogenation, specifically adding hydrogen to an aldehyde to produce an alcohol. The mass of hydrogen to be added is 4.45% of the mass of the aldehyde. The remaining steps involve algebraic equations to determine the molar mass of the aldehyde and the resulting alcohol. The conversation ends with a discussion about experimental data and its accuracy.
  • #1
lioric
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Homework Statement
The mass of an alcohol by the way of hydrogenation of a coresponding aldehyde is 4.45% higher than the mass of the aldehyde. Find the mass of the aldehyde
Relevant Equations
Aldehyde + H2 = alcohol
Ethanal + H2 = ethanol
Aldehyde + H2 = alcohol
Ethanal + H2 = ethanol
This is all that I have done so far
 
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  • #2
4.45% of the mass of the aldehyde is the mass of what you are adding to the aldehyde.
All that's left is the Algebra.
 
  • #3
.Scott said:
4.45% of the mass of the aldehyde is the mass of what you are adding to the aldehyde.
All that's left is the Algebra.
In hydrogenation, we add only hygrogen
So meaning we are adding 4.45% mass of the aldehyde worth of hydrogen. Let me try
 
  • #4
.Scott said:
4.45% of the mass of the aldehyde is the mass of what you are adding to the aldehyde.
All that's left is the Algebra.
Let's say x=100
X+H2 = 100+4.45
100+4.45=104.45
This is what I got. I'm sort of lost here

I sort of get this question as have an x g of aldehyde
Add 4.45% of x g of hydrogen to it and we get 4.45% g higher alcohol.
But I'm stuck with the algebra
 
  • #5
Let's say that X is the mass of the aldehyde.
X+mass(H2) = what function of mass(alcohol)?
 
  • #6
.Scott said:
Let's say that X is the mass of the aldehyde.
X+mass(H2) = what function of mass(alcohol)?
X+2=(4.45/100) x (X)+X
Is this ok?
We could say x=100
100g + 4.45g= 104.45g
 
Last edited:
  • #7
Assuming you used 1 mole of hydrogen (what was its mass?) what has to be the molar mass of the aldehyde?
 
  • #8
The mass referred to here is molar mass. Going from alcohol to aldehyde represents a loss of two hydrogens. Let X be the molar mass of the aldehyde and X+2 be the molar mass of alcohol.

The ratio of (X+2)/X = what?

molar mass alcohol / molar mass aldehyde = what? in this example...
 
  • #9
chemisttree said:
The mass referred to here is molar mass. Going from alcohol to aldehyde represents a loss of two hydrogens. Let X be the molar mass of the aldehyde and X+2 be the molar mass of alcohol.

The ratio of (X+2)/X = what?

molar mass alcohol / molar mass aldehyde = what? in this example...
0.0455
When that is multiplied with 100 we get 4.45%
 
  • #10
Almost. The value of that ratio is 1 + 0.0445 or 1.0445

Do you see that if the numerator is greater than the denominator the result must be > 1?

Solve for X
 
  • #11
chemisttree said:
Almost. The value of that ratio is 1 + 0.0445 or 1.0445

Solve for X
Yes because it's an increase right?

X+2/x = 1.0445
X+2=1.0445x
1.0445x-x=2
0.0445x=2
X=2/0.0445
X=44.94
 
  • #12
That molar mass corresponds to which aldehyde? Consider only C,H&O in the formula.
 
  • #13
chemisttree said:
That molar mass corresponds to which aldehyde? Consider only C,H&O in the formula.
The lowest formula of aldehyde is HCOH
Mass of HCOH= 30
44.94/30=1.498
 
  • #14
Nope. Keep trying. This formula wt is not 30... it is ~45.
 
Last edited:
  • #15
chemisttree said:
Nope. Keep trying. This formula wt is not 30... it is ~45.
CnH2n+1CHO
So CH3CHO mass = 44
44.94/44=1.02
 
  • #16
Close enough!
 
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  • #17
chemisttree said:
Close enough!
Close enough?
What was the error here?
 
  • #18
There was no error on your part. Sometimes the data we get from an experiment isn’t perfect, isn’t exact. The data from this example was only off from theoretical by 2%. That’s usually good enough. Close enough!
 
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  • #19
chemisttree said:
There was no error on your part. Sometimes the data we get from an experiment isn’t perfect, isn’t exact. The data from this example was only off from theoretical by 2%. That’s usually good enough. Close enough!
Thank you very much
You teaching technique is awesome. I really learned a lot.
PS. There is one more question that I have posted could you take a look at that too please

Here is the link
https://www.physicsforums.com/threa...f-a-hydrocarbon-using-combustion-data.990753/
 

1. What is an aldehyde?

An aldehyde is a type of organic compound that contains a carbonyl group (C=O) bonded to at least one hydrogen atom. It is characterized by its distinct odor and is commonly found in many natural and synthetic substances.

2. Why is it important to find the mass of an aldehyde?

The mass of an aldehyde is important for various reasons. It can help determine its purity, identify the compound, and calculate its molar mass for further chemical reactions. It is also necessary for accurate measurements in experiments and industrial processes.

3. How do you find the mass of an aldehyde?

The mass of an aldehyde can be found by using a balance or scale to measure the weight of a given sample. The sample is usually in the form of a liquid or solid and is placed on the balance, which will display the mass in grams.

4. Can the mass of an aldehyde change?

Yes, the mass of an aldehyde can change depending on various factors such as temperature, pressure, and chemical reactions. However, the molecular mass of the compound remains constant and can be used to determine the mass of a given sample.

5. Are there any safety precautions to consider when handling aldehydes?

Yes, aldehydes can be hazardous if not handled properly. They are flammable and can cause irritation to the skin, eyes, and respiratory system. It is important to use proper protective equipment and follow safety guidelines when working with aldehydes.

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