chem mcq...

[MHHaider707]

after heating metal nitrate changes to metal oxide (xo)which must be 5-3.2 because air escape out now equate the mole of metal nitrate and metal oxide and find ar of metal tally it with the element in databooklet!

Can you do the working? im still not getting the answer

2Ca(NO3)2 ------> 2CaO + 4NO2 + O2

Now Mr of Ca(NO3)2 = 164 and moles of Ca(NO3)2 = (5/164)

?If 2 moles of Ca(NO3)2 gives 4 moles of NO2 and 1 mole of O2

then (5/164) moles of Ca(NO3)2 will give 2x(5/164) moles of NO2 and (5/164)/2 moles of O2

Now the lost mass is the total mass of O2 and NO2 given off!!!

So Lost mass = (moles of NO2 x Mr of NO2) + (moles of O2 x Mr of O2)
= (2x(5/164) x 46) + ((5/164)/2 x 32)
= 2.8 + 0.49
= 3.29 g

So answer is C i-e Calcium!!!

 

[alisha]

oh finally got it thanx!