The number of hydroxyl ions in 10cm3 of 0.2M HCl solution is 1)5×10^-4 2)3×10^8 3)3×10^12 4)5×10^-12

Dear Student,

To solve this, we need to find the number of moles of hydroxyl ions. To find that, we need to find the concentration of hydroxyl ions.


HCl is a strong acid. So it dissociates completely.

So, H+=0.2 MpH = -logH+=0.6989pKw=pH+pOHpOH=14-0.6989pOH=13.3012=-log[OH-]So, [OH-]=antilog[-13.3012]=4.98 x 10-14 MNow, Molarity of OH-ions = 4.98 x 10-14 MVolume = 10 cm3=10 ml=0.01 LSo,Number of moles = Molarity x Volume =  4.98 x 10-14  x 10-2=4.98 x 10-12 So, number of ions = number of moles x NA=4.98 x 10-12 x6.022 x 1023=29.989x 1011=2.99 x 10123 x 1012
Thus, the number of hydroxyl ions is 3 x 1012.
Thus, the correct answer is option (3)

Hope it helps.


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