An aqueous solution of Pb(NO3)2 is made by placing 275 g of solid Pb(NO3)2 into a volumetric flask and adding water to the 1.00 L mark (assume that 775g of water has been added to achieve this total solution volume). (Assume MW of Pb(NO3)2 = 331g/mole) A) What is the molarity (M) of this solution? B) What is the molality (m) of this solution? C) What is the mass % of Pb(NO3)2 in this solution? D) What is the mole fraction of Pb(NO3)2 present in this solution?

A) 0.831 M

B) 1.07 m

C) 26.2%

D) 0.0189

Explanation:

A) First we convert the mass of Pb(NO₃)₂ to moles:

Then we divide it by the total volume (1.00 L) to calculate the molarity:

B) We convert the grams of water to kilograms:

Then we divide the Pb(NO₃)₂ by the kilograms of water:

C) We divide the mass of Pb(NO₃)₂ by the total mass of the solution:

D) We calculate the moles of water:

Then we divide the Pb(NO₃)₂ moles by the total number of moles:

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !