Simple equation: sulfuric acid and lithium hydroxide

Question

10.0 grams of solid lithium hydroxide is added to an aqueous solution of sulfuric acid. How many grams of lithium sulfate can be produced?

i wrote the equation: 2LiOH (s) H2SO4 (aq) >> Li2SO4 (aq) 2H2O (l)

then i multiplied 10.0 grams by 109.95 grams (molecular mass of Li2SO4) and divided that by 47.9 grams (molecular mass of 2LiOH) and got 23 grams of Li2SO4. So is it right? Also are my phases of matter correct as well?

Answer 1

2LiOH (s) + H2SO4 (aq) >> Li2SO4 (aq) +  2H2O (l)

Note the molar ratios 2:1::1:2

Calculate the moles of LiOH

Moles(LiOH) = 10g/24(Mr of LiOH) = 0.41666.. moles

Moles(Li2SO4) = 0..41666... / 2 = -.208333.... moles

Mass(Li2SO4) = 0.2083333 x 110 = 22.916666...g

NB

1. Your Mr(Relative molecular mass) for LiOH is incorrect. It is:-

Li x 1 = 7 x 1 = 7

O x 1 = 16 x 1 = 16

H x 1 = 1 x 1 = 1

7 + 16 + 1 = 24 ( or 23.95 - half of your figure).

2. In the 2nd line of my calculation, note the moles is divided by 2. This because 0.41666... moles is equivalent to '2' from the formula.

However the product (LiSO4) has a molar ratio of '1'. So the moles of LiOH must be divided by '2' to give the moles of Li2SO4. When calculating masses and products, always convert everything to moles.

Your indication of phases correct.

NNB

Because Li2SO4 is aqueous, to check the mass of product, the water in the system must be driven off by using an evaporating dish. Tare weigh an evaporating dish. Weigh the evaporating dish with everything in it. Drive off the water and reweigh, (when it contains only white crystals).  The difference between tare weight and crystal weight of the evaporating dish is the mass of product (Li2SO4).

Answer 2

That is not right, the answer is 11.4 grams, you forgot mole ratio, every two moles of LiOH is to one mole of Li2SO4. Everything else is correct.

Do the "fence post" method to get all the unit right.  

Answer 3

Moles LiOH  =10.0 g /23.948 g/mol =  0.418

the ratio between LiOH and Li2SO4 is 2:1

moles Li2SO4 = 0.418 /2 = 0.209

Mass Li2SO4 = 0.209 mol x 109.95 g/mol = 23.0 g

Phases of matter are correct