Pb(SO4)2 + 4 LiNO3 -> Pb(NO3)4 + 2 LiSO4. How many moles of Lithuim nitrate will be needed to make 250g of Lithuim sulfate?

Answer 1

Your chemical reaction equation is not correct. It should be:

Pb(SO₄)₂ + 4LiNO₃ → Pb(NO₃)₄ + 2Li₂SO₄ (added the 2 subscript after the "Li")

Step 1) Calculate the molar mass of Li₂SO₄ (lithium sulfate)

Li: 6.941 x 2 = 13.882

S: 32.066 x 1 = 32.066

O: 15.999 x 4 = 63.996

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109.944 g/mol

So (250 g)/(109.944 g/mol) = 2.274 moles

Notice that your balanced chemical reaction equation says it takes twice as many moles of LiNO₃ as it does Li₂SO₄ (it takes 4 moles of LiNO₃ to every 2 moles of Li₂SO₄)

So if there are 2.274 moles of Li₂SO₄ then you must have started with twice that many moles of LiNO₃ and 2.274 x 2 = 4.548 moles

Rounding to 2 sig figs gives us 4.5 moles of LiNO₃