Entry Journal 10/31 1.Calculate the number of grams in 5.6 moles of Na 3 PO 4 . 2.How many L of O 2 gas are in 7.5 moles of O 2 ?
Jan 05, 2016
Entry Journal 10/311. Calculate the number of grams in 5.6 moles
of Na3PO4.
2. How many L of O2 gas are in 7.5 moles of O2?
Chapter 9Stoichiometry:
The calculation of chemical quantities in chemical
reactions.
Stoic. Survival Kit:• To be successful in this chapter you will need
to:– Balance Chemical Equations– Convert from
• Moles molecules• Moles grams• Moles liters (@ STP)
Stoic. Study Recommendations
• Do the homework the night it is assigned.
• Ask homework questions in class.
• Go back to your homework and fix problems.
• Participate whiteboard exercises
• Practice makes Proficient
Look at Balanced EquationsC5H12(g) + O2(g) CO2(g) + H2O(g)
• Lets look at:– Atoms (just like balancing the equation)– Molecules/formula units– Moles– mass
• The only two that are conserved (same on both sides) are atoms and mass!
1C5H12(g) + 8O2(g) 5CO2(g) + 6H2O(g)
• Most important relationship:
• 1 mole of C5H12(g) reacts with 8 moles of O2(g) to form 5 moles of CO2(g) and 6 moles of H2O(g)
• We used the balanced equations to come up with conversion factors.
Mole-Mole Calculations• Chemical equations provide more
information than we have had before. We can now relate moles of product to moles of reactant in mathematical equations.
1C5H12(g) + 8O2(g) 5CO2(g) + 6H2O(g)
• Mole ratio: A conversion factor derived from the coefficients of a balanced equation.– *** This means that you must ALWAYS check to see if
the equation given is balanced…– Used when you want to relate different chemicals
• Some mole ratios:
1C5H12(g) + 8O2(g) 5CO2(g) + 6H2O(g)
• How this shows up in chemistry:• Example: How many moles of water are
produced when 4 moles of oxygen are reacted?
• Example: How many moles of pentane are needed to produce 12 moles of CO2?
Some Practice:• Al(s) + O2(g)Al2O3(s)
• Write the six mole ratios that can be derived from the equation.
• How many moles of Al are needed to form 3.7 moles of Al2O3?
• ** hint: balance the equation first!!
Al(s) + O2(g)Al2O3(s)
• How many moles of O2 are required to react with 14.8 moles of Al?
• How many moles of Al2O3 are formed with 0.78 mole O2 reacts with Al?
Remember this?
mol
atomsx
1
1002.6 23
The MOLE
Mass (g)Molecules, atoms,
formula units
atomsx
mol231002.6
1massmolar
1mol
mol1
massmolar
Volume (L)
L
mol
4.22
1
mol
L
1
4.22
Remember this? Let’s add more…
mol
atomsx
1
1002.6 23
The MOLE
Mass (g)Molecules, atoms,
formula units
atomsx
mol231002.6
1massmolar
1mol
mol1
massmolar
Volume (L)
L
mol
4.22
1
mol
L
1
4.22
Relate Chemical A toChemical B
xA yB
ymolB
xmolA
Now we can do many more calculations
• Most common calculation: Mass Mass
• It isn’t that much harder, as long as you remember your stuff from chapter 7.
• Hints: – You ALWAYS need to balance the equation.– Use the mole ratio when you need to change
chemicals.
1C5H12(g) + 8O2(g) 5CO2(g) + 6H2O(g)
• How this shows up in chemistry:• Example: How many moles of water are
produced when 20.5 grams of oxygen are reacted?
• Example: How many grams of oxygen gas are needed to react if 2.8 moles of water are formed?
1C5H12(g) + 8O2(g) 5CO2(g) + 6H2O(g)
• Example: How many grams of water will be formed when 552.3 grams of C5H12 are reacted in the presence of oxygen gas?
KClO3 KCl + O2
How many molecules of O2 are produced by the decomposition of 6.54 grams of KClO3?
CO(g) + O2(g) CO2(g)
• How many liters of O2 are required to burn 3.86 liters of CO?
NO2 + H2O NO3 + NO• How many grams of NO2 must react with
water to produce 5.00 x 1023 molecules of NO?
CaC2 + H2O C2H2 + Ca(OH)2
• How many grams of C2H2 are produced by adding water to 5.00 g of CaC2?
• How many moles of CaC2 are needed to react completely with 49 g of water?