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F322 OCR Chemistry- January 2010
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for question 3d, why couldn't u mention evaporation? isn't this the same as non standard conditions? also for 5dii why couldn't u say metal? and for 7b-why couldn't u say reforestation. and for 7c why couldn't u say the graphs are similar?
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(Original post by runny4)
for question 3d, why couldn't u mention evaporation? isn't this the same as non standard conditions? also for 5dii why couldn't u say metal? and for 7b-why couldn't u say reforestation. and for 7c why couldn't u say the graphs are similar?
for question 3d, why couldn't u mention evaporation? isn't this the same as non standard conditions? also for 5dii why couldn't u say metal? and for 7b-why couldn't u say reforestation. and for 7c why couldn't u say the graphs are similar?
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If some of the fuel evaporated, then n(fuel) would have been larger, so -Q/n (=delta H) would be smaller, i.e. less exothermic.
If some of the water evaporated, delta T would be larger (since m in m c delta T would be smaller (without you knowing)), this would lead to a larger value of delta H. BUT how much water would evaporate (as a percentage of 100 g)? Given all the other reasons for error, this would be a tiny effect.
Non-standard conditions essentially refers to starting at 25oC, which this experiment didn't (23.7). This doesn't matter, since we're measuring delta T. 4.2 J of energy raises 1 g of water by 1 K, regardless of whether the water starts at 25oC or 50oC.
I have some sympathy for wanting to suggest a metal, e.g. Mg, which could do the job. We certainly wouldn't use Mg but this is due to the source of metals, such as Mg - MgO or MgCO3 (which we can dig up out of the ground). Why would we want to electrolyse MgO to get Mg, just to react it with HCl (and make MgCl2) when we could react the MgO with HCl (still making MgCl2)?
Would reforestation be something "research chemists" would do?
The two graphs are not similar... one charts CO2 vs age, t'other change in T vs age.
If some of the water evaporated, delta T would be larger (since m in m c delta T would be smaller (without you knowing)), this would lead to a larger value of delta H. BUT how much water would evaporate (as a percentage of 100 g)? Given all the other reasons for error, this would be a tiny effect.
Non-standard conditions essentially refers to starting at 25oC, which this experiment didn't (23.7). This doesn't matter, since we're measuring delta T. 4.2 J of energy raises 1 g of water by 1 K, regardless of whether the water starts at 25oC or 50oC.
I have some sympathy for wanting to suggest a metal, e.g. Mg, which could do the job. We certainly wouldn't use Mg but this is due to the source of metals, such as Mg - MgO or MgCO3 (which we can dig up out of the ground). Why would we want to electrolyse MgO to get Mg, just to react it with HCl (and make MgCl2) when we could react the MgO with HCl (still making MgCl2)?
Would reforestation be something "research chemists" would do?
The two graphs are not similar... one charts CO2 vs age, t'other change in T vs age.
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(Original post by Pigster)
If some of the fuel evaporated, then n(fuel) would have been larger, so -Q/n (=delta H) would be smaller, i.e. less exothermic.
If some of the water evaporated, delta T would be larger (since m in m c delta T would be smaller (without you knowing)), this would lead to a larger value of delta H. BUT how much water would evaporate (as a percentage of 100 g)? Given all the other reasons for error, this would be a tiny effect.
Non-standard conditions essentially refers to starting at 25oC, which this experiment didn't (23.7). This doesn't matter, since we're measuring delta T. 4.2 J of energy raises 1 g of water by 1 K, regardless of whether the water starts at 25oC or 50oC.
I have some sympathy for wanting to suggest a metal, e.g. Mg, which could do the job. We certainly wouldn't use Mg but this is due to the source of metals, such as Mg - MgO or MgCO3 (which we can dig up out of the ground). Why would we want to electrolyse MgO to get Mg, just to react it with HCl (and make MgCl2) when we could react the MgO with HCl (still making MgCl2)?
Would reforestation be something "research chemists" would do?
The two graphs are not similar... one charts CO2 vs age, t'other change in T vs age.
If some of the fuel evaporated, then n(fuel) would have been larger, so -Q/n (=delta H) would be smaller, i.e. less exothermic.
If some of the water evaporated, delta T would be larger (since m in m c delta T would be smaller (without you knowing)), this would lead to a larger value of delta H. BUT how much water would evaporate (as a percentage of 100 g)? Given all the other reasons for error, this would be a tiny effect.
Non-standard conditions essentially refers to starting at 25oC, which this experiment didn't (23.7). This doesn't matter, since we're measuring delta T. 4.2 J of energy raises 1 g of water by 1 K, regardless of whether the water starts at 25oC or 50oC.
I have some sympathy for wanting to suggest a metal, e.g. Mg, which could do the job. We certainly wouldn't use Mg but this is due to the source of metals, such as Mg - MgO or MgCO3 (which we can dig up out of the ground). Why would we want to electrolyse MgO to get Mg, just to react it with HCl (and make MgCl2) when we could react the MgO with HCl (still making MgCl2)?
Would reforestation be something "research chemists" would do?
The two graphs are not similar... one charts CO2 vs age, t'other change in T vs age.
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