Hi I'm doing OCR B salters and have no idea how to learn all the information... It seems like when I do the past papers the information I need is completely new to me. How do I tackle this, especially for the F332 paper?
hi guys. just wondering if anyone can help me on question 6 of this worksheet pls. Have no clue how to start it.
Have you got a)? For the second part they tell you the enthalpy change per mole, so if you work out the MR of butane then divide it by the enthalpy (in kJ) then you have the mass of butane required to produce 1 kJ of energy through combustion
Have you got a)? For the second part they tell you the enthalpy change per mole, so if you work out the MR of butane then divide it by the enthalpy (in kJ) then you have the mass of butane required to produce 1 kJ of energy through combustion
Hi!! Was wondering if anyone could help out with some AS chemistry? My question is, why do halogenoalkanes combust more incompletely than alkanes/alcohols etc, and why do iodoalkanes combust less easily than for example bromoalkanes? The explanation my teacher gave was that because the halogens were heavier atoms, they are a larger proportion of the molecule as a whole, which I get, but not how that relates to the combustibility... If someone could explain that'd be great!! Thanks
When you go to AQA's website for the latest papers (2009-2013) you'll see on the left hand side that it says 'older papers'.
When you read the older papers, there are some things that aren't on the spec for Unit 1 anymore (such as reagent tests, solubility, alkali and acids) so you should ignore them - other than that, they're excellent and I've found it a great way to revise after you've written up, or are doing, your notes.
The 2014 paper is harder than most, it's the paper that's had the most maths in for a while - other than that, it's no different and in some sections it's really nice.
just want to ask if you have got the 2014 paper on you... if so can you send it to me please.... much appreciated because i really want to get an A in AS chemistry... ive done notes and now im going through all the practice questions after each section, after that im gonna start doing some past paper....do you think i should do more and is the enough for me to get an A??? thanks in advance for all your help
Hi!! Was wondering if anyone could help out with some AS chemistry? My question is, why do halogenoalkanes combust more incompletely than alkanes/alcohols etc, and why do iodoalkanes combust less easily than for example bromoalkanes? The explanation my teacher gave was that because the halogens were heavier atoms, they are a larger proportion of the molecule as a whole, which I get, but not how that relates to the combustibility... If someone could explain that'd be great!! Thanks
Chlorine, for example, does not form a particularly stable oxide. In the process of burning halogenated hydrocarbons the halide must either become hydrogen halides (reducing the enthalpy of reaction overall) or free halogens, which also reduces the overall enthalpy change.
Hi!! Was wondering if anyone could help out with some AS chemistry? My question is, why do halogenoalkanes combust more incompletely than alkanes/alcohols etc, and why do iodoalkanes combust less easily than for example bromoalkanes? The explanation my teacher gave was that because the halogens were heavier atoms, they are a larger proportion of the molecule as a whole, which I get, but not how that relates to the combustibility... If someone could explain that'd be great!! Thanks
Don't take my word for it, but I think it's because halogenoalkanes have less branching than alkanes?? I'm pretty sure branching is a factor in combustion efficiency, something to do with it having less Van Der Wall's forces, so less bonds to break and less heat required. The idoalkanes is because iodine has more electrons than bromine so it's more likely to induce a temporary dipole (VDW's). More VDW's, more heat energy required to break the bonds.
Chlorine, for example, does not form a particularly stable oxide. In the process of burning halogenated hydrocarbons the halide must either become hydrogen halides (reducing the enthalpy of reaction overall) or free halogens, which also reduces the overall enthalpy change.
Okay thanks, that makes sense! But surely reducing the enthalpy change would make it easier for the reaction to take place, as it requires less energy?
Don't take my word for it, but I think it's because halogenoalkanes have less branching than alkanes?? I'm pretty sure branching is a factor in combustion efficiency, something to do with it having less Van Der Wall's forces, so less bonds to break and less heat required. The idoalkanes is because iodine has more electrons than bromine so it's more likely to induce a temporary dipole (VDW's). More VDW's, more heat energy required to break the bonds.
Yeah I'm not sure about the branching, doesn't the halogen just replace one of the hydrogens? I'll have to look into the VDWs thing, thanks
Okay thanks, that makes sense! But surely reducing the enthalpy change would make it easier for the reaction to take place, as it requires less energy?
hi please can someone help me with this question 9 1.12 g of iron reacts with oxygen to form 1.60 g of an oxide of iron. Use relative atomic masses: Fe = 56, O = 16. What is the formula of this oxide of iron? A FeO5 B Fe2O10 C Fe3O2 D Fe2O3 i originally got a but it is wrong and i don't know why thanks