Volumetric analysis question. Help

k3l

volumetric analysis question. Help plz

hi ppl. i need help on a chem question:

5.00mL of conc. H2SO4 was pipetted into a volumetric flask containing water and the volume made up to exactly 1.00L. Three 20.00mL samples of 0.200molL^-1 NaOH required 22.30, 22.16, 22.17 and 22.18 mL of the acid for neutralisation using phenolphthalein indicator.
Determine the concentration of the conc. sulfuric acid solution.

thx

k3l

ok, don't worry about the first question... solved

but here is another question...
what is a specific gravity?
its like this...
Concentrated Sulfuric acid contains 98% by weight of pure acid and has a specific gravity of 1.80... what does this mean?

dextercioby

Homework Helper
I think,knowing the value for mass volumic density of $H_{2}SO_{4}$,that that 1.80 is nothing but the mass volumic density of the sulphuric acid's sollution...

Daniel.

k3l

well, its only part of the question

Gokul43201

Staff Emeritus
Gold Member
For the first problem I get about 3.6 M.

Specific gravity is the same as relative density, which is the same number as the density in cgs units. So, the density of the concentrated sulfuric acid solution is 1.8 g/mL. From this (if required) you can also determine the density of pure sulfuric acid, which will be slightly greater than 1.8 g/mL (since the density of the 2% that is water will be 1.0 g/mL).

Gokul43201

Staff Emeritus
Gold Member
k3l, if you need help with specific problems, you must show what you've tried. We can not help unless we know that you are making an effort. Too many people come here without making even a first attempt. From your second post, it's obvious that you're working on the problem yourself, but we wouldn't have known that from reading the first post.

k3l

ok, actually its a simple question (i think lol)
the whole question is like this:
Concentrated Sulfuric acid contains 98% by weight of pure acid and has a specific gravity of 1.80. a certain volume of this is added to water and the volume made up to 500.0mL. a mean titre of 19.60mL of this diluted acid solution neutralises 20.00mL of 0.1000molL^-1 potassium hydroxide solution.
Determine the volume of concentrated acid used in the dilution.

i've solved like... up to the concentration of Sulfuric acid in the 500.0mL sample, but without knowing what does it meant by "has a specific gravity of 1.80"... i couldn't get any further.

here is what i got for the concentration of H2SO4 in 500mL sample: 5.102*10^-2molL^-1

dextercioby

Homework Helper
Okay,the answer is good.Now you need to find the volume of concentrated $H_{2}SO_{4}$ used in the sollution.I don't know in which the one of 500mL,or 19.6mL...

Anyway,u have the concentration and the volume,you can find the number of moles of $H_{2}SO_{4}$ and then the mass.Knowing the density,u can find the volume...

Daniel.

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