Hi everyone,
One of my GCE O Level Chemistry Sec 4 student from Anglo Chinese School (ACS) sent emailed me a challenging O Level Chemistry Multiple Choice Question (MCQ) and i would like to share it with you.
At first look, it seems to be a very challenging tricky question since you would not know which chapter / topic does the question belongs to. I was contemplating between using essential concepts from either ENERGY CHANGES (Exothermic & Endothermic) or TRENDS IN PERIODIC TABLE to answer the question.
Let’s take a look at the question:
Question 1:
Hi sean, I came across this question and I would like to know the answer.
Which pair of elements, described by their proton number, will react together most exothermically?
A. 1 and 8
B. 3 and 10
C. 9 and 19
D. 12 and 16
Suggested answer and reasoning by my student as follows (i always encourage my student to analyze the question for possible answers and propose it, before asking me for an answer, cos that is how they learn effectively):
I know for sure that B is wrong since proton number 10 is for an unreactive noble gas. My guess is 12 and 16, because both are 2+ and 2-, so the overall charge is greater than the rest.
Which is the correct answer? And on what basis do I use to determine the correct answer?
So all Chemistry students out there (be it GCE O Levels,? GCE A Levels, IGCSE, IB and IP Chemistry), what is your take?
Feel free to give your answers & reasoning in the “LEAVE A REPLY” section below. I would love to hear from you.
PS: I will come in at later stage to give my suggested answer and reasoning
GUYS I am confused
i think that this wuestion may have more than 1 answer!!
we should look into references to make sure that one of them is right
i think that(1) is right because this envolves oxygen
but i am not totally sure
if someone knows the answer and sure of it then plz contact me cuz i need that very much
i wish u luck with your exams
Option a, because hydrogen(1) reacts with oxygen to produce water and it is an exothermic process
Hi I somehow accidentally stumbled onto this page, but is the answer [C]?
For Highly Exothermic may mean that the reaction between the two elements would be very reactive and high amount of energy would be released.
For option C, Flourine is the most reactive halide element as it is at the top of group VII while potassium is the most reactive in the Reactivity Series, so that leads me to conclude that by reacting two highly reactive elements together, the amount of energy that is being produced would be a lot.
Option B is definitely out in my opinion for reacting elements with a noble gas would not produce high amount of energy, if not, no reaction?
Option D would produce less amount of energy as compared to option C, for the metal used is magnesium and magnesium is less reactive than potassium. Sulphur is also less reactive than flourine. Am I correct?
What I am not really sure is option A, for it involved oxygen. If the reaction between oxygen and hydrogen involves combustion, then wouldn’t the amount of energy released be a lot?
Mind correcting me if I am wrong. Thanks alot anyway:)
Options C & D are between metal and a non-metal where transfer of electrons take place. B a reaction cannot take place one of them is an inert gas. But A is between non metals and electron affinity is very high for these two elements therefore exothermic
I’m confiused.First explain me that does amount of heat produced in a reaction
depends upon the reactants valency or reactivity.
the cOrrect answer is C. i.e 9[fluorine] with 19[potassium]..coz both the elements in their series are at the tOp like fluorine [the most reactive halogen] and potassium the most reactive in metal reactive series!
although i`m not that gud at this subject,but still i wanna give it a try!
accordin to me,its option C. i.e 19[Potassium] with 9[Fluorine],as potassium lies on
the tOp position in the reactivity series and therefore is most reactive metal,and with
it fluorine is also the most reactive non-metal in group VII,the reaction b/w an alkali metal and halogen is very active as both elements are on their top positions.Ionic Bond will be formed
b/w the two which`l b quick and more exothermic
it can`t be magnesium and sulphur because cOmparatively these elements are less active
than 9 n 19!
this is what i think is right!
You can’t tell if proton number 12 (magnesium) with 16 (sulfur) actually gives an exothermic reaction; even then, 1 (hydrogen) with 8 (oxygen) is a combustion reaction, hence it is highly exothermic. Combustion reactions are highly exothermic, so option A is most likely the answer.