13 Responses

1. JO.

   06|Aug|2008 1

   Hi.

   a) carbon dioxide, lead(II) nitrate and water.
   PbCO3(s) + 2HNO3(aq) –> H2O(l) + CO2(g) + Pb(NO3)2(aq)

   b) spectator ions: 2H+, 2NO3-, Pb2+
   PbCO3(s) + 2H+(aq) –> H2O(l) + CO2(g) + Pb2+(aq)

   PS: could you tell me which metals normally have different roman symbols in front of them? I have noticed that metals like copper have a roman symbol in front, in the case of copper(II) sulphate.

   Thank you very much.

   Reply

   

   sean Reply:
   November 2nd, 2008 at 2:45 pm

   Hi Jo,

   Glad you tried the question. There is a saying “Wanting leads to Wanting, Doing leads to Having”.

   Part (a) – correct state symbols, and stoichiometry for the balanced chemical equations. Well done!

   Part (b) – Ionic Equations is correct. However, the answer for Spectator Ions is not fully correct.

   Spectator Ions are defined as ions that does not take place in the chemical reactions. They are there just to stabilize the reaction.

   In this case, only NO3-(aq) ions is Spectator Ions. Meaning the other 2 ions you have mentioned, H+(aq) and Pb2+(aq) are involved in the chemical reaction, and not Spectator Ions.

   PS Reply: Only compounds made from metals of the Transition Block have roman symbols in their chemical name. This is because they have variable oxidation states.

   Cheers
   Sean

   Reply

2. sean

   08|Aug|2008 2

   Hi Jo,

   Glad you tried the question. There is a saying “Wanting leads to Wanting, Doing leads to Having”.

   Part (a) – correct state symbols, and stoichiometry for the balanced chemical equations. Well done!

   Part (b) – Ionic Equations is correct. However, the answer for Spectator Ions is not fully correct.

   Spectator Ions are defined as ions that does not take place in the chemical reactions. They are there just to stabilize the reaction.

   In this case, only NO3-(aq) ions is Spectator Ions. Meaning the other 2 ions you have mentioned, H+(aq) and Pb2+(aq) are involved in the chemical reaction, and not Spectator Ions.

   PS Reply: Only compounds made from metals of the Transition Block have roman symbols in their chemical name. This is because they have variable oxidation states.

   Cheers
   Sean

   Reply

3. karissa

   22|Oct|2008 3

   Which cation can make an insoluble product with Cl– in water?

   Reply

   

   sean Reply:
   October 23rd, 2008 at 8:53 pm

   Hi Karissa,

   Refer to my previous post on Table of Solubility of Salts.

   http://simplechemconcepts.com/chemistry-question-solubility-of-common-salts/

   For GCE O Level N Level, IB Program and ICGSE, there are 2 cations in your syllabus that will form insoluble salts with chlorides.

   There are Ag+ and Pb2+, to form insoluble AgCl (s) and PbCl2 (s) respectively.

   Hope this helps. Let me know if you understand it.

   Cheers
   Sean =)

   Reply

4. kelvini

   21|Sep|2009 4

   send me O level calculations of mole and electrolysis please.

   Reply

5. ircha

   15|Oct|2009 5

   this is so useful. i dont get a thing in class! sigh!

   Reply

6. Kendrick

   13|Dec|2009 6

   Hi Sir,

   I have attempted a few mole calculation questions and I am stuck with one question.

   The question simply ask me to calculate:

   the mass of one calcium atom

   I am unsure how to do it. Can you please guide me?

   Thank you very much =)

   Reply

   

   Saud Reply:
   March 1st, 2010 at 1:33 am

   Hi Kendrik,

   im not a teacher but still i guess i can tell you about it…………

   when we say about 1 mole of a substance, we mean to mention its 6.02 X 10 power 23 particles of it………………….

   so for one atom i-e one particle of it first we should find its moles by dividing 1 by the avogadro’s number i-e 6.02 X 10 power 23………….

   then by simple formula of moles= mass/molar mass

   mass= molar mass X moles

   we know the molar mass of calcium = 40
   and (calculated) moles of one atom of calcium = 1.661129568106312292358803986711 power negative 24

   then by multiplying 40 by the mole number

   40 X 1.661129568106312292358803986711 = 6.6445182724252491694352159468439 power negative 23 grams……

   hope you did not felt humiliated

   Reply

7. Saud

   01|Mar|2010 7

   being a carbonate CO2 is sure, others are Lead Nitrate and water

   as for the balanced equation:-

   PbCO3(s) + HNO3(aq) ——> PbNO3(aq) + CO2(g) + H2O(l)

   for the spectator ions:-
   NO3 (-1) aq

   the equation would be

   PbCO3(s) + H (+1)(aq) —–> Pb (+2)(aq) + CO2(g) + H2O(l)

   Reply

   

   sean Reply:
   May 6th, 2010 at 12:17 am

   Hi Saud,

   Something not right with your Chemical Formulae of Lead (II) Nitrate.

   As such, your balanced chemical equation and ionic equation is incorrect.

   Regards,
   Sean Chua

   Reply

8. Sarah

   04|Mar|2010 8

   hello sir,
   i have a simple chemistry question which i have solved but i am not quite sure of the answer:

   Q: how many atoms of hydrogen are there in 0.75 moles of ammonia?
   Ans:
   no. of molecules of ammonia = 0.75*6.02*10^23
   no of atoms of hydrogen = 3*0.75*6.02*10^23
   =1.35*10^24

   is it correct?

   Reply

   

   sean Reply:
   May 6th, 2010 at 12:19 am

   Hi Sarah,

   In view that 1 molecule of ammonia contains 3 hydrogen atoms, i believe your working is correct!

   Keep Learning,

   Sean Chua
   Master Trainer & Author

   Reply