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Number of elements in the fourth period = 27
For a given value of l, number of elements= 3(2 l+1)
This clearly gives 3+9+15 = 27 for the fourth period
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Q1 if tehre were three possible values (-1/2,0,1/2) for spin quantum number s,then the number of elements in fourth preiod of periodic table would be ?
Q2 what indiactor is uded fr titration of 0,1 M KH2BO3 and 0.1M HCl ?
(ans given is methyl red.My dbt is do we ahve to learn pH range of all indicators ???phenolapthaein and methyl orange are common but methyl red isnt [2][2])
Q3 A mixture containing CO and CO2 (ingaseous state) exert pressure of 1 atm at 25 C.EnoughO2 is added to double the pressure.Subsequent passage of a spark results in pressure increase to 2.56 atm and temp increase t o175 C.Assuming ideal behaviour,what % of original moles was CO ?
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24btw kalyan..whats the source of this equation
""For a given value of l, number of elements= 3(2 l+1) ""
29actually wen s can have only two values ( 1/2 and -1/2) then the total no of electrons in a subshell is 2*(2l+1)..
so in the question s can have three values so i guess he modified the eqn in this way...
29In qn 3
i assumed the volume of the container to be such that there is 1 mole of mixture of gases present in it at 25C
CO = x moles CO2 = 1-x moles
Subsequent passage of a spark coverts all molecules of CO to CO2
2CO + O2 → 2CO2
x x/2 x
so acc. to the first assumption N moles of gas will exert N atm pressure at 25C
so in the second step 1 mol of O2 is added according to the abv assump.
we are given the pressure exerted by the final mixture is 2.56 atm at 175C ..i converted it to temp 25C so the pressure exerted will be 1.7 atm
that meanis 1.7 moles of the gases are present finally
in the final mixture no. of moles of CO2 = 1-x + x =1
so no. of moles of oxygen left is 0.7
no of moles of oxygen used is 0.3
no. of moles of CO present initially = 2* 0.3 = 0.6
so % of CO initially = 60%
the method is a li'l bit confusing ..will try to post a shorter solution