1. Is STP supposed to be 0C 20C or 25C ?

2. I didn't understand anything

3. What is 760

4. What is 273

57 minutes ago, HbWhi5F said:

1. Is STP supposed to be 0C 20C or 25C ?

2. I didn't understand anything

3. What is 760

4. What is 273

I recognise 273K as 0C and I recognise 760mmHg as standard atmospheric pressure expressed, in old fashioned style, in millimetres of mercury.

The IUPAC definition of STP specifies 0C, i.e 273K (actually 273.15K to be exact but nobody bothers with that detail) and 1 bar (100kPa).

But exactly what they are trying to do here is unclear to me from the snippet you have provided. In particular I don't see where mmHg comes in. I feel there must be some extra text that discusses this.

1 hour ago, exchemist said:

But exactly what they are trying to do here is unclear to me from the snippet you have provided. In particular I don't see where mmHg comes in. I feel there must be some extra text that discusses this.

By inference, P₁ is also in mmHg.

They're simply applying PV/T = constant with arbitrary units. Pressure units could equally well be in hundredweight force per acre providing they're consistent on both sides of the equality.

37 minutes ago, sethoflagos said:

By inference, P₁ is also in mmHg.

They're simply applying PV/T = constant with arbitrary units. Pressure units could equally well be in hundredweight force per acre providing they're consistent on both sides of the equality.

Oh yes now I see. Thanks.

So, to spell it out for @HbWhi5F , they say p(1).V(1)/T(1) = p(stp).V(stp)/T(stp) and rearrange to get just V(stp) on one side of the equation:

p(1).V(1)T(stp)/T(1).p(stp) = V(stp)

and then insert values of 273K for T(stp) and 760mmHg for p(stp).

So evidently they are measuring p(1) with a mercury manometer. It might have been clearer if we had access to the figure 8.15 that the text refers to.

On 10/9/2025 at 10:16 PM, exchemist said:

Oh yes now I see. Thanks.

So, to spell it out for @HbWhi5F , they say p(1).V(1)/T(1) = p(stp).V(stp)/T(stp) and rearrange to get just V(stp) on one side of the equation:

p(1).V(1)T(stp)/T(1).p(stp) = V(stp)

and then insert values of 273K for T(stp) and 760mmHg for p(stp).

So evidently they are measuring p(1) with a mercury manometer. It might have been clearer if we had access to the figure 8.15 that the text refers to.

Isn't @HbWhi5F in the habit of acknowledging assistance freely given? Or is it a case of cost nowt ergo worth nowt.

1 hour ago, sethoflagos said:

Isn't @HbWhi5F in the habit of acknowledging assistance freely given? Or is it a case of cost nowt ergo worth nowt.

We did have a discussion about that. I’ve decided to give him or her the benefit of the doubt for a bit. We’ve established this person is using Indian textbooks written in English but I don’t know how easy they find conversing in English.

1 hour ago, exchemist said:

We did have a discussion about that. I’ve decided to give him or her the benefit of the doubt for a bit. We’ve established this person is using Indian textbooks written in English but I don’t know how easy they find conversing in English.

... I guess typing "Shukria" is against site rules.

5 hours ago, sethoflagos said:

... I guess typing "Shukria" is against site rules.

You might think that. I couldn't possibly comment.😉

@sethoflagos @exchemist thank you

1. In standard gibs energy 25C is used are STP.

2. what does multiplying with 760 and 273 achieve.

@sethoflagos sorry sometimes I take time to reply and my English is good, that is Arabic for thank you you wrote not any Indian language 😀

2 hours ago, HbWhi5F said:

@sethoflagos @exchemist thank you

1. In standard gibs energy 25C is used are STP.

2. what does multiplying with 760 and 273 achieve.

@sethoflagos sorry sometimes I take time to reply and my English is good, that is Arabic for thank you you wrote not any Indian language 😀

Surely that would be shukran?My understanding is shukriya, or shukria, means thank you in Urdu and possibly in Hindi as well. As least, it was widely used by people from S Asia when I lived in Dubai, including by my Goan secretary.

To your question, it seems they are taking STP to be 273K and 760mmHg. This seems consistent with the IUPAC convention, though there are others, as you can read here: https://en.wikipedia.org/wiki/Standard_temperature_and_pressurehttps://oxfordre.com/planetaryscience/planetaryscience/display/10.1093/acrefore/9780190647926.001.0001/acrefore-9780190647926-e-145

The purpose of the multiplication is stated in the text you originally pasted. It converts the measured volume change into a volume at STP.

The purpose of that is so you can calculate how many moles of gas have been generated: https://chem.libretexts.org/Courses/Heartland_Community_College/CHEM_120%3A_Fundamentals_of_Chemistry/06%3A_Gases/6.11%3A_STP

You are quite right that standard Gibbs Free Energies are generally quoted at 25C (298K). This is annoying I agree, but it is the way it is.

2 hours ago, exchemist said:

Surely that would be shukran?My understanding is shukriya, or shukria, means thank you in Urdu and possibly in Hindi as well. As least, it was widely used by people from S Asia when I lived in Dubai, including by my Goan secretary.

Exactly my understanding too. These are the normal English transcriptions of the Arabic, Hindi, and Urdu scripts respectively.

How does this conversion multiplication works ?

@exchemist Dhanyavad

58 minutes ago, HbWhi5F said:

How does this conversion multiplication works ?

@exchemist Dhanyavad

It is in my second post of 9th October. As @sethoflagos pointed out, it utilises the principle that pV/T = constant.

Edited October 16Oct 16 by exchemist

@exchemist sorry struggling with thermodynamics

33 minutes ago, HbWhi5F said:

@exchemist sorry struggling with thermodynamics

OK it wasn’t my favourite thing at first either. I got used to it.

But pV/T = constant means p1V1/T1 must equal p2V2/T2, right? So if you have p1, V1 and T1 from your experiment, you can set that equal to pSTP.VSTP/TSTP , and since pressure and temperature at STP are standard, they are given, so you just need to find V STP, by rearranging.

The thing is you know that, for any gas, 1 mole at STP occupies 22.4litres. So once you have converted the volume you have measured experimentally into litres at STP, you know how many moles were generated by the reaction.