joebf86
05-07-2005, 02:40 PM
7.12g of an mixture were added to 50cm3 of 1 M hydrochloric acid and when the reaction was complete,the solution was diluted to 250cm3 with distilled water.
25cm3 fo this diluted solution required 24.4cm3 of 1 M sodium hydroxide for neutralisation of the excess acid.
Assuming all the basic material in the mixture to be magnesium hydroxide,calculate thethe percentage of magnesium hydroxide in the mixture.
can anyone help me with this. i tried but still couldnt get an acceptable answer.
my solution:
Mg(OH)2 + 2HCl ----> MgCl2 + 2H2O
number of moles in 50cm3 HCl= 50x1
1000
= 0.05 mol
for the dilution part, is it correct to use M1V1=M2V2?
so it should be 1x50=m2 x 250
m2= 0.2 mol dm^-3 ?
as for neutralisation, i should use
HCl + NaOH ---> NaCl + H2O?
M acid x V acid = 1
M basex V base 1
the M and V for base is confirm 24.4 cm3 and 1 mol dm^-3
so we should subsitute which for the acid part?
M=0.2 V=? OR M=? V=25
till here i m really confused. maybe the steps above are wrong,
can anyone help me with this?
25cm3 fo this diluted solution required 24.4cm3 of 1 M sodium hydroxide for neutralisation of the excess acid.
Assuming all the basic material in the mixture to be magnesium hydroxide,calculate thethe percentage of magnesium hydroxide in the mixture.
can anyone help me with this. i tried but still couldnt get an acceptable answer.
my solution:
Mg(OH)2 + 2HCl ----> MgCl2 + 2H2O
number of moles in 50cm3 HCl= 50x1
1000
= 0.05 mol
for the dilution part, is it correct to use M1V1=M2V2?
so it should be 1x50=m2 x 250
m2= 0.2 mol dm^-3 ?
as for neutralisation, i should use
HCl + NaOH ---> NaCl + H2O?
M acid x V acid = 1
M basex V base 1
the M and V for base is confirm 24.4 cm3 and 1 mol dm^-3
so we should subsitute which for the acid part?
M=0.2 V=? OR M=? V=25
till here i m really confused. maybe the steps above are wrong,
can anyone help me with this?