Concentrated sulfuric acid (98.12 g.mol-1) has a density of 1.5 g/cm3 and is 60 % H2SO4 per mass. The rest is water. How many H+ ions are there in a 45ml concentrated sulfuric acid solution?

1 Answer
Mar 30, 2017

Answer:

There are approx. #5xx10^23# individual hydronium ions.......

Explanation:

We need to find (i) #[H_2SO_4]#, the concentration with respect to #"sulfuric acid"#.

And so we start with a #1*cm^3# volume, which has a mass of #1.5*g#, of which 60% by mass is the acid, i.e. #0.90*g# with respect to sulfuric acid.

And so #"concentration"# #=# #"moles"/"volume"# #=# #((0.90*g)/(98.08*g*mol^-1))/(1.0xx10^-3*L)#

#=9.18*mol*L^-1# WITH RESPECT TO #H_2SO_4(aq)#.

And thus (ii) in a #45*mL# volume, there are #45xx10^-3Lxx9.18*mol*L^-1=0.413*mol# with respect to #H_2SO_4#.

Given that the acid is DIPROTIC, there are thus #0.826*mol# with respect to #H_3O^+# or #H^+#.

To get the number of #H_3O^+# ions, we multiply this quantity by the #"Avocado number"#, i.e.

#0.826*molxx6.022xx10^23*mol^-1=4.97xx10^23# hydronium ions.