# Suggest with reasons, to which group of the Periodic Table element X b

## Homework Statement

Element X forms a chloride, XCln which melts at 3$$\circ$$C. When 0.500 g of the chloride reacts with an excess of acidified silver nitrate, 1.19g of AgCl are formed.

Another 0.500g sample of the chloride is heated strongly and chlorine gas is given off. When the residue is treated with an excess of acidified silver nitrate, only 0.714g of AgCl is precipitated.

(1) Predict the type of bonding in XCln.
(2) Suggest with reasons, to which group of the Periodic Table element X belongs.
(3) Calculate the value of n and attempt to identify X.

## The Attempt at a Solution

(1) It is covalent because of the low melting point.

(2) I would say group 5 or 6 because the chlorides exhibits several valencies. (but i don't know which one to choose) and the question asks for reasonS<---

(3) I am completely lost and confused. I calculated the number of mol of AgCl formed in both cases knowing that the difference between these values should give me something important. but i don't know what.

and i think X is phosphorous because PCl5 decomposes into PCl3 on heating. but the question does not ask for this kind of reasoning.

## Answers and Replies

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Borek
Mentor
If it is XCl3, and if 0.500 g contains the same amount of chlorine as 1.19 g of AgCl, what is molar mass of X?

chemisttree
Homework Helper
Gold Member
...and i think X is phosphorous because PCl5 decomposes into PCl3 on heating. but the question does not ask for this kind of reasoning.
MP (with sublimation) for PCl5 is 100oC.

Use the total #moles of Cl to determine the atomic weight of X possible for n=1,2,3,4,5,6,7,8.
You will note that n=1 is unlikely since upon heating, some Cl remains behind. Two Cl-'s have changed from chloride to Clo (an oxidation) The X must have been reduced by an equal amount.

After heating you have some Cl left. Use the total #moles of Cl that remain after heating to determine the atomic weight of X possible for the new "n"=1,2,3,4,5,6,7,8,...

Any overlap?

Borek
Mentor
Sorry, no idea where have I read this 3 in XCln

But the idea remains the same, just - as chemisttree wrote - calculate molar masses for different values of n.

it is not phosphorous then...

i understood what you meant, i already found the possible Ar of X for XCln.

but i need the mass of the residue after heating (it is no longer 0.5g because some Cl has been liberated from it). how can i find that?

does (1.19 - 0.714) give you the mass of chlorine liberated?

thnks

Borek
Mentor
does (1.19 - 0.714) give you the mass of chlorine liberated?
Indirectly. These are masses of AgCl. But you are on the right track.