GRAM to gram mole ratio stoichemetry pratice #6 worksheet

Question

GRAM TO GRAM MOLE RATIO STOICHMETRY

Copper I iodide , Cul , is not stable enough to last long in storage , so it is generally made just prior to use . In can be prepared from copper sulphate and hydriodic acid by the following reaction . SHOW WORK ! 2 CuSO 4 +4 HI ---->

2 Cul+2H2SO4 +I2 If 34.56 grams of is used calculate the number of grams of each of the products that are produced

Answer 1

Hello, Emily,

The questions wants to know how many grams of each product will be produced if we start with 34.56 grams of CuSO₄. We will need to assume that all of it reacts, which means there is sufficient HI to complete the reaction. We can answer this after we convert the information into units of moles. We could use the actuual number of molecules written out, but it's a pain. 34.56 grams of CuSO₄ contains 1.30x10²³ molecules of CuSO₄. We can say the same thing using a different unit, moles. A mole is shorthand for 6.02x10²³ of anything. 34.56 grams of CuSO₄ can be converted to moles by dividing the mass by it's molar mass of CuSO₄. (34.56 grams CuSO₄)/(159.6 grams CuSO₄/mole) = 0.0.2165 moles CuSO₄. Chemists quickly liked the idea of writing 0.0265 moles instead of 1.30x10²³ molecules, and a new unit was born. Book publishers were especially happy. Long story, sorry.

The next step is to determine how many moles of the products will form from 0.02165 moles of CuSO₄. That answer is revealed in the balanced equation:

2CuSO₄ + 4HI ---->2Cul + 2H₂SO₄ + I₂

CuI: The equation tells us we'll get 2 moles CuI for every 2 moles CuSO₄ we react. That's a molar ratio of 1/1. That means we'll get an amount of CuI that is equal (1:1) to the number of reactant molecules. So we'll get 0.2165 moles of CuI. Convert that to grams by multiplying by the molar mass of CuI: (0.2165 moles CuI)*(190.5 grams/mole CuSO₄) = 41.24 grams CuI.

I₂: Use the same logic. The molar ratio to CuSO₄ is (1/2 moles I₂/moles CuSO₄). This means we'll produce (1 mole I₂/2 moles CuSO₄)*(0.2165 moles CuSO₄) = 0.1083 moles I₂. Convert to grams by myltiplying by iodine's molar mass of 253.8 grams/mole (diatomic). That gives us 27.5 grams of I₂.

H₂SO₄: Same process. Molar ratio is 1:1, so we should get 0.2165 moles of H₂SO₄, which is equal to 21.23 grams.

(4 sig figs)

Bob