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Chemistry: Post your doubts here!
Easiest to visualise statements 1 and 3 using the energy diagrams. Statement 2 can be known to be true from background knowledge, or we can use the energy diagram on the left. Since it takes more energy to break the C(solid) of graphite into C(gas), we can infer that the C-C bonds of graphite... -
Chemistry: Post your doubts here!
:) I kind of agree. So long as you see that the application of concepts is correct, then theres no need to worry. This was a question I was looking for, from W12_qp12 I think using bond energy of N2 as 994kJ/mol will give us the answer A, while using 944kJ/mol will not give us any of the... -
Chemistry: Post your doubts here!
Yup. That's my point. For students attempting much older past year papers, they will see that the bond value of N2 is 994 instead of 944. There's no need to be alarmed or overthink, the concepts and applications remains the same. Good luck! -
Chemistry: Post your doubts here!
It really depends on the years, last time it was 994. For example, qn 19 of 2003. http://papers.xtremepapers.com/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20(9701)/9701_w03_qp_1.pdf It became 944 in the more recent years. -
Chemistry: Post your doubts here!
I can't say for sure why it differs in this specific case. I were to guess, it could be that recent experiments and calculations done in the labs gave a more updated value. -
For now, it would be at most 2008- 2013
For now, it would be at most 2008- 2013- Metanoia
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Unfortunately, it is unlikely I would have the time to prepare more videos in the near future...
Unfortunately, it is unlikely I would have the time to prepare more videos in the near future. Any more videos would have to be added at the end of the exams, for the next batch of students.- Metanoia
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Chemistry: Post your doubts here!
The values might be different due to the different editions of data booklets. -
Chemistry: Post your doubts here!
Nov 05. Qn3. The easiest way is first figure out the respective elements in the four options, then refer to the 2nd IEs in IE table in the data booklet. A. Mg (compare its 2nd IE to Na and Al) B. Al (compare its 2nd IE to Mg and Si) C. Si (compare its 2nd IE to Al and P) D. P (compare its 2nd... -
Chemistry: Post your doubts here!
Nov 04 Qn 34: The marking scheme says all statements are correct. So statement 1 is also correct. May 05 Qn 3: Element in D belongs to Group V (the huge increase in IE is from the 5th to the 6th IE) Qn14: Reactivity of Group II metals increases down the group , calcium is more reactive than... -
Chemistry: Post your doubts here!
ii) moles of KOH used = vol. of KOH solution x conc. of KOH solution = 0.01 dm^3 x 2 mol dm^-3 = 0.02 mol iii) from equation mol of Al : mol of KOH 2 : 2 Therefore, 0.02 mol of KOH would react with 0.02 mol of Al. iii) mass of Al reacted = moles of Al x Ar of Al = 0.02 x 27 = 0.54 g -
Chemistry: Post your doubts here!
Q3. Ti+ --> Ti3+ + 2e- moles of Ti+ : moles of e- : moles of VO3- 0.003 moles : ? : 0.002 moles 3 moles : ? moles : 2 moles Using the half equation, we can see that 3 moles of Ti+ will transfer 6 moles of electrons to 2 moles of VO3-. In other words, 1 mole of VO3- gains 3 moles of electrons... -
Biology; Chemistry; Physics: Post your doubts here!
Both Ca(OH)2 and CaO are bases. They will react with ammonium salt to produce NH3 CaO + (NH4)2SO4 --> CaSO4 + H2O + 2NH3 Ca(OH)2 + (NH4)2SO4 --> CaSO4 + 2H2O + 2NH3- Metanoia
- Post #19,807
- Forum: O-Levels / GCSEs / IGCSE
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Chemistry: Post your doubts here!
The suggested answer, while conceptually correct, has not answered the question totally. It's more of explaining why the melting point of Group I metals decreases down the group rather than why Group I metals on the whole has a low melting point. To answer the second point, we need to bring in... -
Chemistry: Post your doubts here!
Writing out the equations for both of them based on the definitions, we can see that they are the same. H2(g) + 1/2 O2(g) --> H2O (l) -
Biology; Chemistry; Physics: Post your doubts here!
Actually, I would disagree. CaO would react with the ammonium fertilizer base + ammonium salt --> salt + water + NH3 The above equation is the concept being tested in this question So using CaO would result in nitrogen nutrient being lost in the form of NH3. It is thus better to use CaCO3...- Metanoia
- Post #19,806
- Forum: O-Levels / GCSEs / IGCSE
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Chemistry: Post your doubts here!
From [CO32-]/[HCO3-] = 0.958, we have [CO32-] = 0.958[HCO3-] moles of H+ used = 0.2 x 22/1000 = 0.0044 mol moles of H+ used = 1 x moles of HCO3- + 2 x moles of CO32- = 1 x moles of HCO3- + 2 x 0.985 moles of HCO32- = 2.97 moles of HCO3- =0.0044 mol moles of HCO3- = 0.0044/2.97 = 0.0014815... -
Chemistry: Post your doubts here!
s08qp1 Just use proportion if its easier to visualise. mass of N in 100 g of fertiliser = 15 g mass of N in 14 g of fertiliser = (15/100) x 14= 2.1 g moles of N in 14 g of fertiliser = 2.1 /14 = 0.15 mol conc of N in 5 dm^3 of solution = 0.15/5 = 0.03 mol/dm^3 Q15 CaCO3 --> CaO + CO2... -
Chemistry: Post your doubts here!
Login off now. Its 1 am here. :eek: All the best to you guys for the paper! -
Chemistry: Post your doubts here!
s11qp12 Q10. There are many maths approach, but i think least stressful is to do trial and error with the 4 options and tally with the Mr. Q29. Perhaps you can show how many chiral carbons (and where) you are getting, then we can see whats missing? Q33. Equation 2 is out. pV= nRT, not MRT...