3. Balance the following chemical equation. (5pts) MgCl2 (aq) + KOH (aq) Mg(OH)2
ID: 547961 • Letter: 3
Question
3. Balance the following chemical equation. (5pts) MgCl2 (aq) + KOH (aq) Mg(OH)2 KCI + 4. Based on the above balanced chemical equation, answer the following questions thcalculations lead to your answer. No points will be given if you only state a) If 80.0g of magnesium chloride is used, how many grams of potassium hydroxide are theoretically needed to complete the reaction? (5pts) b) If 80.0 grams of magnesium chloride and 50.0g of potassium hydroxide are mixed to React, 1) which will be the limiting reagent, MgClz or KOH and why? (5pts) 2) how many grams of Mg(OH)2 will be produced theoretically? (5pts) 3) If actually 19.5g of Mg (OH)z is produced, what is the percent yield of Mg (OH)2? (5pts)Explanation / Answer
Equation shows that 1 mole of MgCl2 reacts with 1 mole KOH to form 1 mole Mg(OH)2 and 1 mole KCl.
a. Molecular weight of MgCl2=> molar mass of magnesium + 2* molar mass of chloride => 24+2*35.5 = 24+71= 95 grams/mole
Molecular weight of KOH= molar mass of potassium+ molar mass of Oxygen+molar mass of hydrogen
= 39+16+1= 56 grams/mole
Hence, for 80 grams of MgCl2, number of moles= 80g/95g/mol=> 0.84 moles
so, KOH needed => 0.84 moles= 0.84 moles* 56 gram/mole= 47.04 grams
b)
1. we have already calculated that for 80.0 g of MgCl2, we will require 47.0 grams of KOH.
Hence, if we have 50.0 grams of KOH to react, only 47.0 grams will be enough to react and exhaust MgCl2. Hence, MgCl2 is the limiting reagent.
2. In this case, MgCl2 will be the limiting reagent and by using logic and given equation, we know Mg(OH)2 produced theoretically is equal to moles of MgCl2 reacted i.e. 0.84 moles.
Molecular weight of Mg(OH)2 => molder mass of magnesium+ 2*molar mass of Oxygen+ 2*molar mass of hydrogen=>
24+2*16+2*1=> 24+32+2=> 58 grams/moles
so, Mg(OH)2 produced=> 58 g/mol*0.84 moles=> 48.7 grams
3. Actual Mg(OH)2 produced=> 19.5 g
Then, percent yield of Mg(OH)2 => actual yield/ theoretical yield
=> 19.5g/48.7g=> 0.400=> 40% yield
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