[Nadee]

Dear friends,

I am trying to balance a chemical equation for Compressed natural gas (CNG) when mixed with air. But I am unable to balance it, since my background is not chemistry.
What I understood till now is CNG has maximum composition of Methane (CH4). So, I calculated using it, but the teacher is saying that I need to use all composition of CNG and balance the equation. I really need your help as I researched for it, but I couldn't find it anywhere. Please see the attachment. I need to balance in this way.

Need your help as soon as possible. Thank you very much in advance.

Kind regards

[Borek]

It is not possible to balance an equation for a mixture.

It is possible to express the process using something that looks like a reaction equation (like you did), but it is not something that classifies as a balanced equation. Not sure what your teacher means.

[Nadee]

Dear Borak,

Ok, for instance now, If you get this question, how will you solve such question ?
The way I did with just Methane (CH4), I used methane quantity as 1 kg. And we know that CNG is composition of Methane, Ethane and propane. what if we divide 1 kg with these 3 quantities with respect to the percentages CNG has these 3 elements. Is it possible ?
But I found little information about making balanced equation for methane only, I tried alot for CNG but couldn't find. please see attachment.
Even if you know how to solve this problem in your way, your answer is most welcome.

Thank you.
Kind regards

[AWK]

You must know the content of all flammable gas components (volume or mass percentage) and balance the combustion reactions for each component separately.

[Nadee]

You must know the content of all flammable gas components (volume or mass percentage) and balance the combustion reactions for each component separately.

Dear AWK,
I agree with you. I know the composition of CNG, but I dont have any experience with such questions, I have never worked before. Actually because of pandemic they have included this subject and no classes has been taken for it. They are expecting us to do by our-self. But if one of you help me in calculating for CNG, I will get an idea how to solve it. Also i have to perform with LPG later which I will do on my own once you help me with CNG.

Kind regards

[AWK]

You don't need much experience here. If you can balance one equation, then you can probably balance the next one. In this respect, hydrocarbon combustion reactions are very easy. Finally, you must add the results of all reactions.

[Nadee]

You don't need much experience here. If you can balance one equation, then you can probably balance the next one. In this respect, hydrocarbon combustion reactions are very easy. Finally, you must add the results of all reactions.

Dear AWK,

That is what I am unable to do, If I don't know something I will learn right here from one of you. I will be very grateful if you could write the reactions for me. Remaining calculations I will do on my own. I am confused with these reactions.

Kind regards

[billnotgatez]

@Nadee
If you look at the forum rules then you will see that AWK is staying within them.
If you post what you think the equation is then we will let you know the correctness.

[Nadee]

You don't need much experience here. If you can balance one equation, then you can probably balance the next one. In this respect, hydrocarbon combustion reactions are very easy. Finally, you must add the results of all reactions.

Dear AWK,

Thanks for your reply. I tried to perform hydrocarbon combustion reactions for Methane, Ethane and propane. And i searched for composition on one of the website. The composition of Methane is 94.7% , Ethane is 4.2 %, and propane is 0.2 % in CNG. There is butane and pentane as well but they are 0.02 and 0.01 in %. But I think the calculations will be too long. So I am considering only important 3 gases (Methane as 95%, ethane as 4.5% and propane as 0.5%).
So, if we divide them in 1 kg as mentioned in my question. Methane will be 0.95 kg, ethane as 0.045 kg and propane as 0.005 kg )
Is this the correct way to perform calculations ?
And also you mentioned that I need to add all the results of all reactions together. Please see the attachment. You mean to say that I need to add all these ''total'' together for further calculation of flame temperature

Please correct me where I am wrong. Eagerly waiting for your response.

Thank you for cooperating.
Kind regards

[AWK]

About 3.7 kg of CO₂ can be obtained from 1 kg of pure coal. You have over 8 kg of 1 kg of gas containing less carbon.

[Nadee]

About 3.7 kg of CO₂ can be obtained from 1 kg of pure coal. You have over 8 kg of 1 kg of gas containing less carbon.

Dear AWK,

You are seeing over 8 kg of CO2 because I considered propane as only 0.005 kg in 1 kg of CNG combustion process & I performed this reaction independently for each gas as you said, this is something I want to know, where I am going wrong and how to correct it or what is the proper way to solve it ?
How to add all the reactions I have performed so that it should be combustible with 20% of excess air ?

Kind regards 

[AWK]

Your final total CO₂ result must be around 3.7 kg.

[Nadee]

Your final total CO₂ result must be around 3.7 kg.

Dear AWK,
Only if you say the value of CO2 is 3.7 kg which is correct, how can I get it until & unless you don't say where I am going wrong, some hints on how to solve it properly or where I did wrong will be beneficial. Your suggestions are most welcome.

Kind regards

[AWK]

You have 950 grams of methane, 45 grams of ethane, and 5 grams of propane. Balance the combustion with oxygen only. Thanks to this you won't get lost when adding water and CO₂. Remember that the reactions are balanced in moles. You also have a molar air composition. The transition from moles of oxygen to air, and then to excess air is already a very simple calculation.

[Nadee]

You have 950 grams of methane, 45 grams of ethane, and 5 grams of propane. Balance the combustion with oxygen only. Thanks to this you won't get lost when adding water and CO₂. Remember that the reactions are balanced in moles. You also have a molar air composition. The transition from moles of oxygen to air, and then to excess air is already a very simple calculation.

Dear AWK,

No, I cannot neglect Nitrogen I think. This calculation has to be performed with 21% O2 and 79% Nitrogen as air composition which must be mixed with CNG with 20 % of excess air. Please see the attachment.

Kind regards