Pre stoichiometry
2Li + ZnF2 -> 2LiF + Zn
What is the mole ratio of Li to Zn?
2:1
Fe2O3 + 3 C → 3 CO + 2 Fe
If 220 grams of C are reacted, how many grams of CO will be produced?
510 grams CO
what is percent yield
Percent yield is the amount of a compound obtained from a chemical synthesis reaction with respect to the theoretically expected amount. This is a percentage value.
2Li + ZnF2 -> 2LiF + Zn
If I have 3.2 moles of LiF, how many grams is that?
234.62 g
C2H4 + 3 O2 → 2 CO2 + 2 H2O
If 379.33 grams of O2 are reacted, how many grams of CO2 will be produced?
347.81 grams CO2
Some underwater welding is done via the thermite reaction, in which rust (Fe2O3) reacts with aluminum to produce iron and aluminum oxide (Al2O3). In one such reaction, 258 g of aluminum and excess rust produced 464 g of iron. What was the percent yield of the reaction?
464 g = actual yield
Fe2O3 + 2 Al --> Al2O3 + 2 Fe
% yield = Actual/theoretical x 100
87%
2Li + ZnF2 -> 2LiF + Zn
If I have 550 grams of ZnF2, how many moles of ZnF2 do I have?
5.32 moles ZnF2
AlCl3 + 3 H2O → Al(OH)3 + 3 HCl
If 1.6 grams of H2O are reacted, how many grams of AlCl3 will also be reacted?
3.9 grams AlCl3
HNO3 + KOH → KNO3 + H2O
When 261.7 grams of HNO3 are reacted with 343.71 grams of KOH, 267 grams of KNO3 are produced. What is the percent yield of this reaction?
Correct answer is 63.59%
• 100% yield would be 419.9 grams KNO3
• HNO3 is the limiting reagent
2Li + ZnF2 -> 2LiF + Zn
If I begin with 6.75g of Li and excess ZnF2, how many moles of Zn can be produced in the chemical reaction above?
0.49 moles Zn
2 Al + 3 H2SO4 → Al2(SO4)3 + 3 H2
If 198.68 grams of Al2(SO4)3 are produced, how many grams of H2 will also be produced?
3.5117 grams H2
If 292 grams of NO are reacted with 439 grams of NH3, how many grams of H2O will be produced if the reaction proceeds with a 53.1% yield?
4 NH3 + 6 NO → 5 N2 + 6 H2O
Correct answer is 93.1 grams H2O
• 100% yield would be 175 grams H2O
• NO is the limiting reagent
2Li + ZnF2 -> 2LiF + Zn
How many grams of ZnF2 would be required to produce 2.21 moles of LiF in a chemical reaction?
114.23 g ZnF2
Pb + 2 AgNO3 → Pb(NO3)2 + 2 Ag
If 19.320 grams of AgNO3 are reacted, how many grams of Pb(NO3)2 will be produced?
18.835 grams Pb(NO3)2
How many grams of PF5 can be formed from 9.46 g of PF3 and 9.42 g of XeF4 in the following reaction?
What is the limiting reagent of
2PF3 + XeF4 ---> 2PF5 + Xe
PF3 ⇒ 9.46 g / 87.968 g/mol = 0.10754 mol
XeF4 ⇒ 9.42 g / 207.282 g/mol = 0.045445 mol
2) Determine limiting reagent:
PF3 ⇒ 0.10754 / 2 = 0.05377
XeF4 ⇒ 0.045445 / 1 = 0.045445
XeF4 is limiting