"emmisions puzzle"

[imamartian]

this letter was in the paper last week.... intriguing question.. any of you guys work it out?

"Petrol has a specific gravity of 0.74 a litre and thus weighs 740g. My petrol car does 31mpg, which equates to 11km per litre. This means it consumes 740g of petrol in 11km, equivalent to 67g per kilometre. However, the manufacturer and the DVLA tell me that the same car produces carbon dioxide at the rate of 235g/km. I learnt in my school physics lessons that matter cannot be created or destroyed, so how can this car produce a gas weighing nearly four times the weight of the raw material?"

 

[WDIK]

you are forgetting, that you dont just use the fuel, it has to react with oxygen to promote combustion.
CO2 is one part carbon from the fuel, and two parts oxygen, from induced air.

 

[imamartian]

isn't that just three of the four parts??????

 

[blondini]

and the atomic weight of oxygen is greater than that of carbon.
The atomic weight of carbon is around 12 and oxygen around 16. THerefore each carbon atom (12) contributes to one CO2 molecule that has an equivalent weight of 42. C12 + O(2x16) = 42.

 

[blondini]

isn't that just three of the four parts??????

Dunno how much of that litre of petrol is hydrogen that becomes water when it burns, but also don't know how they calculate the CO2 g/km for a vehicle. Is it based on urban or combined mpg? Is your 31mpg real or is it manufacturers figure? It sounds good for a 235g/km vehicle.

 

[tim west]

The fourth parts it burns is the biggest, it's called money

 

[joe-90]

You don't calculate the CO2 emission - you stick a hose over the exhaust and measure it. How can you argue with that?

 

[Softus]

I learnt in my school physics lessons that matter cannot be created or destroyed...

You weren't listening then, because I was told, and am repeatedly reminded by (amongst other sources) populist TV science magazines, that matter and energy are interchangeable.

so how can this car produce a gas weighing nearly four times the weight of the raw material?"

Why do you even give a sh*t?

 

[imamartian]

I learnt in my school physics lessons that matter cannot be created or destroyed...

You weren't listening then, because I was told, and am repeatedly reminded by (amongst other sources) populist TV science magazines, that matter and energy are interchangeable.

It wasn't me. As i said, i quoted a letter in the paper.

so how can this car produce a gas weighing nearly four times the weight of the raw material?"

Why do you even give a sh*t?

Why do you need to be rude about it? If you're not interested, don't reply.

 

[Softus]

I learnt in my school physics lessons that matter cannot be created or destroyed...

You weren't listening then, because I was told, and am repeatedly reminded by (amongst other sources) populist TV science magazines, that matter and energy are interchangeable.

It wasn't me. As i said, i quoted a letter in the paper.

Quite so. I misunderstood - apologies.

The answer, in that case, is that the letter writer is both wrong and misguided.

 

[imamartian]

Accepted.

And i suspect you're right about that. Just wanted to see if anyone on here could unravel the writer's logic...

 

[blondini]

You don't calculate the CO2 emission - you stick a hose over the exhaust and measure it. How can you argue with that?

Ok then, suppose you measure it. You would have to find a way to remove the other gases in the exhaust from the measure. Not saying it can't be done and not saying they don't do it that way.

What I meant to question was what cycle they use to determine the CO2 emission rating.

 

[joe-90]

Cycles don't emit CO2. Only methane when the rider farts.

 

[blondini]

Cycles don't emit CO2. Only methane when the rider farts.

If you're including the riders emissions then they most certainly do emit CO2

 

[Trazor]

I learnt in my school physics lessons that matter cannot be created or destroyed...

Yes that is right, the total amount of matter and energy in the universe is constant.

You weren't listening then, because I was told, and am repeatedly reminded by (amongst other sources) populist TV science magazines, that matter and energy are interchangeable.

Yes matter and energy are interchangeable, but matter is neither created or destroyed, by the process.

Perhaps you should have listened more, Softus.