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Q. 1.Calculate the number of HCl molecules present in 10ml of 0.1N HCl solution.

Q.2. 4.0g of NaOH are contained in one decilitre of solutions. Calculate mole fraction. Molarity and molality of NaOH. ( Given, density of solution=                                                              1.038g/ cm3)

Q. 3. You are provided with 2 litre each of 0.5 M NaOH and 0.4M of NaOH solutions. What maximum volume of 0.30 M NaOH can be obtained from these solutions without using water at all ?

 

Joshi sir comment

1)   no of miligm eq. = 10*0.1 = 1

so no. of gm. eq. = 1/1000

since acid is monobasic so no. of moles = 1/1000

so molecules = 1/1000 * 6.023 * 1023

 

2)     0.1 litre soln. contains              4 gm. NaOH

       so 1 litre contains                      40 gm. NaOH

       so 1 litre soln. contains              40/40 moles of NaOH  = 1 mole so molarity = 1

 

 now 1 litre soln. contains                       40 gm NaOH

so 1*1038 gm soln. contains               40 gm. NaOH                   here 1038 gm/litre is density

so 1038 gm. soln. contains                  40 gm. NaOH

so 1038-40 gm. solvent contains        40 gm. NaOH

so 998 gm. solvent contains                 40 gm. NaOH = 1 mole 

so 0.998 Kg solvent contains                 1 mole NaOH

so molality = 1/0.998 

 

998 gm water contains                   40 gm. NaOH

so 998/18 mole water contains    40/40 mole NaOH

so mole fraction of NaOH = [40/40]/{[40/40]+[998/18]}

 

Third part is irrelevent without using water

 

 

 

Read 3 Solution.

ANS 1)  AS V KNOW N= M X n-factor  & HCl is monobasic means it's n-factor is 1 . so v can find molarity ( i.e. M =normality.)

          NOW USE FORMULA M=( No. of moles of solute X 1000*)/10  (*REMEMBER IT IS IN ml SO CONVERT IT INTO L )

          FROM THIS U WILL GET NO. OF MOLES & NOW U CAN FIND NO. OF HCl molecule( BY USING  1 MOLE = NA )

SARIKA SHARMA 12 year ago is this solution helpfull: 5 6

ANS 2 )  DENSITY  OF SOLUTION IS GIVEN & VOLUME ALSO (DECILITRE) . FROM THIS U CAN FIND MASS OF SOLn

           AS MASS OF NaOH IS GIVEN SO U CAN FIND MASS OF SOLVENT (mass of soln= massof solute + mass of solvent) . MIND THAT OF UNITS

           NOW  USE FORMULA

      a)  M= no. of moles of NaOH / VOLUME OF SOLn

      b)  m= no. of moles of NaOH/ MASS OF SOLVENT IN kg

       c)  MOLE FRACTn=( nA)/ (nA+nB)   where nA & nB= no. of moles of NaOH &H2O RESPT. HERE V WILL TAKE SOLn of NaOH & H2O &  MOLECULAR MASS OF NaOH = 40g & H2O=18g.

SARIKA SHARMA 12 year ago is this solution helpfull: 3 0

ans3) M IS GIVEN FOR BOTH SLUTn  SO FIRST FIND NO. OF MOLES IN EACH ONE  AS U R PROVIDED WITH MOLARITY & VOLUME OF EACH SOLn ). THEN U WILL GET MOLES (TOTAL) NOW ADD THEM & USE THAT NO. OF TOTAL MOLES IN FORMULA , M= NO. OF MOLES (TOTAL) / VOLUME HERE USE M= 0.03 put values 2 find volume

SARIKA SHARMA 12 year ago is this solution helpfull: 3 1

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