[kenny1999]

I encounter a M.C. question, I forgot the values of the quantities but I only concern the concepts... please help

There is a concentrated sulphuric acid with density 9.84g per cm cube, and concentrated sulphuric acid contains 98% by mass of sulphuric acid, how much
sulphuric acid has to be diluted to make 5.00M of 60cm3

Once again I forget all the values so the above numbers are just a make-up... I only remmeber 98%

please teach me how to do. thanks

[AWK]

density 9.84g

Really? - should be a printing error
98 % sulphuric acid shows density 1.84

[Borek]

How many moles do you need for the solution?

What is mass of these moles?

What is volume of concentrated solution that contains this amount?

[kenny1999]

How many moles do you need for the solution?

What is mass of these moles?

What is volume of concentrated solution that contains this amount?

Actually that is a question asking for the volume of sulphuric acid required to make up a certain concentration and volume of sulphuric acid (but I forget the conc. and vol.)

it has given the value of density and it says that concentrated sulphuric acid contains 98% by mass of sulphuric acid. So what I want to know is what does it mean by 98% of sulphuric acid, does it mean for 100g of conc sulphuric acid it contains 98g of sulphuric acid? and how about the given density? What does it mean? I am not sure how to use the value of density as well as the number "98%".

Thanks!

[Borek]

You don't have to guess what percentage concentration means, just use the definition.

I gave you precise outline how to solve the question, try to answer the questions in the given order.

[kenny1999]

You don't have to guess what percentage concentration means, just use the definition.

I gave you precise outline how to solve the question, try to answer the questions in the given order.

sorry I am a little bit confused at the moment

ok , here I would like to ask...


for a conc sulphuric acid with 65% of H2SO4 by mass and has a density of 1.55g/mL
, to calculate the molarity of the solution, do I need to use the value of 65% in the calculation?

am I correct to say..

since there is 1.55g of H2SO4 per 1 mL ( or 1 cm^3)

so molarity = (1.55g/molar mass of H2SO4) / (0.001 L)

do I need to use 65% in calculation? Thanks man

[Borek]

You need to use percentage.

If you have 1mL of the solution its weight is given by the density, but it DOESN'T mean that's the mass of the sulfuric acid. That's mass of a mixture - acid and water.

Check the definition of the percentage concentration.

[kenny1999]

You need to use percentage.

If you have 1mL of the solution its weight is given by the density, but it DOESN'T mean that's the mass of the sulfuric acid. That's mass of a mixture - acid and water.

Check the definition of the percentage concentration.

excuse me , ( i am not using English ), do you mean that instead of representing only the mass of the acid, density is representing mass of sulphuric acid + water per unit mL? if it states 98% (or some other % of sulphuric acid), then i need to multiply 0.98 (or correspondingly other % number) if I want to find the mass of only sulphuric acid per unit mL?

If that's correct, but how about the mobile ions ionized? does 98% (or some other value) include the weight of mobile ion? (i.e. hydrogen ion, sulphate ion)

Thanks you! Thanks you!

[Borek]

do you mean that instead of representing only the mass of the acid, density is representing mass of sulphuric acid + water per unit mL? if it states 98% (or some other % of sulphuric acid), then i need to multiply 0.98 (or correspondingly other % number) if I want to find the mass of only sulphuric acid per unit mL?

Exactly.

If that's correct, but how about the mobile ions ionized? does 98% (or some other value) include the weight of mobile ion? (i.e. hydrogen ion, sulphate ion)

Yes, 98% is the mass fraction of H₂SO₄ - doesn't matter if it dissociated or not (sure it did)