The density of a 15% H2SO4(sulphuric acid) solution is 1.10gm/cm3(1.10gm per centimeter cube).?

Question

calculate molality and molarity.
Molar mass of H2SO4 is 98g/mol.
plz solve this problem and plz explain what does 15%H2SO4 means.

Answer 1

Hai Cm P,

Atomic weight of H: 1.00794g/mol.
Atomic weight of S: 32.065g/mol.
Atomic weight of O: 15.9994g/mol.
=>Molar mass of H2SO4 is 98.0785g/mol.

Molality, Molarity & % denote the concentration of a substance(SOLUTE) in a SOLUTION.

Molality (m or molal) is the number of moles of a given substance(solute) dissolved in one kilogram of solvent(Note: it is solvent & not solution).
Example: 1 molal H2SO4 means 98.0785g H2SO4 of dissolved in 1Kg. of water(solvent)

Molarity(M or molar) is the number of moles of a given substance(solute) dissolved in a litre of solution.
Example: 1 molar H2SO4 means 98.0785g of H2SO4 is present in 1litre of the H2SO4 solution.

% is the mass of a given substance dissolved in one unit-mass of a solution.
15%H2SO4 means The solution has 15% by mass of the solution as H2SO4 and the balance 85% by mass is the solvent(usually water, unless otherwise specified). For instance, 100 gm of 15%H2SO4 comprises of 15gm of H2SO4 & 85gm of water.

Note: There are other measurements of concentration like Mass-volume percentage(% m/v), weight-volume percentage(% w/v), Volume-volume percentage(% v/v), which are different from %, which is actually %m/m, i/ e. mass-mass percentage.



Let, mass of 15% H2SO4 = Mass(Solution) = 100gm. ...assumed for simplicity
Let, density of 15% H2SO4 = Density(Solution) = 1.10gm/cm3. .....remember density varies with temperature & pressure.
Then, volume of 15% H2SO4 = Volume(Solution) = Mass(Solution)/Density(Solution) = 100/1.10 = 90.9091 cm3. = 90.9091/1000 l = 0.0909091 l(litre)


Mass of H2SO4 in the solution = Mass(H2SO4) = (%of H2SO4)X[Mass(Solution)] = 15% X 100 = 15gm. = 0.015Kg.
Mass of Water in the solution = Mass(Water) = Mass(Solution)-Mass(H2SO4) = 100 - 15 =85gm. = 0.085Kg.

Number of moles of H2SO4 in the solution = No(H2SO4) = mass of H2SO4/Molar mass of H2SO4 = 15/98.0785 = 0.1529mole.

By the above data, we can now calculate both Molality & Molarity of 15% H2SO4 with density 1.10gm/cm3.

Molality of the H2SO4 solution = [No(H2SO4)/Mass(Water) in Kg] = 0.1529/0.085 = 1.7993molal.
The solution is called 1.7993m H2SO4 (or 1.7993 molal H2SO4 ).

Molarity of the H2SO4 solution = [No(H2SO4)/Volume(Solution) in litre] = 0.1529/0.0909091 = 1.681899molar.
The solution is called 1.681899M H2SO4 (or 1.681899 molar H2SO4 ).



Hope, this was of little help to you.

Answer 2

Let the sulfuric acid solution be called SA. Assume that 15% means wt/wt, 15g H2SO4 + 85g H2O

Atomic weights: H=1 S=32 O=16 H2SO4=98

1.10gSA/1.00mLSA x 15gH2SO4/100gSA x 1molH2SO4/98gH2SO4 x 1000mLSA/1LSA = 1.68 moles H2SO4 per L solution = 1.68 M

15gH2SO4/85gH2O x 1molH2SO4/98gH2SO4 x 1000gH2O/1kgH2O = 1.80 mole H2SO4 per kg H2O = 1.80 molal

Answer 3

15 Sulfuric Acid

Answer 4

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Answer 5

Doesn't it mean 2 Hydrogens and 4 Sulfiric acids. I'm not too sure.