Quantities in Chemical Reactions

(Part 1)or

Stoichiometry

You’re a car maker now!

Here’s the balanced “equation” for making a car:

1 body + 4 wheels + 2 wipers 1 chem-mobile

Try this:

1 body + 4 wheels + 2 wipers 1 chem-mobile

How many chem-mobiles can you make from 35 bodies?

35.How many chem-mobiles can you make

using 80 wheels?20.How many chem-mobiles can you make

using 98 wiper blades? 49.

What assumption(s) are you making?

1 body + 4 wheels + 2 wipers 1 chem-mobile

For 98 wiper blades, we assume that we haveat least _______ bodies.49; and _______ wheels.196.The “coefficients” in this “equation” are the

equivalent ofmoles in a balanced chemical equation.

Let’s take this to chemistry . . .Li3N(s) + 3H2O(l) NH3(aq) + 3 LiOH(aq)

How many mol of lithium nitride are required to prepare 6 mol LiOH?

2 mol Li3N. Assume

sufficent H2O.

How many mol of water are required to react with 0.5 mol Li3N?

1.5 mol H2O.

Look at ratios in this equation . . .

Li3N(s) + 3H2O(l) NH3(aq) + 3 LiOH(aq)in terms of moles:

1 mol 3 mol 1 mol 3 mol

in terms of mass:

34.8 g 54.1 g 17.0 g 71.9 g

in terms of molecules:6.02E23 18.06E23 6.02E23 18.06E23

formula units molecules molecules formula units

Li3N(s) + 3H2O(l) NH3(aq) + 3 LiOH(aq)

What mass of NH3 is expected from the reaction of 100 g of Li3N with sufficient water?

Li3N(s) + 3H2O(l) NH3(aq) + 3 LiOH(aq)

1 mol Li3N : 1 mol NH3

100 g

↓(/34.82 g·mol-1)

2.87 mol (x 1/1) 2.87 mol

↓(x 17.0 g·mol-1)

48.8 g NH3 expected

What mass of LiOH is expected from the reaction of 100 g of Li3N with sufficient water?

1 mol Li3N : 3 mol LiOH

100 g

↓(/34.82 g·mol-1)

2.87 mol (x 3/1) 8.62 mol

↓(x23.95 g·mol-1)

206 g LiOH expected

If 78.3 g of water is allowed to react with excess lithium nitride, how many molecules of ammonia would be produced?

3 mol H2O : 1 mol NH3

78.3 g

↓(/18.02 g·mol-1)4.35 mol (x 1/3) 1.45 mol

↓(x 6.02E23molec·mol-1)

8.73E23 molecules NH3 expected

Try this one:

What volume of H2(g) at SATP can be obtained from the reaction of 8.54 g of Mg with sufficient HCl(aq)?

Mg(s) + 2 HCl(aq) MgCl2(aq) + H2(g)8.54 g↓(/24.3 g·mol-1)

0.351 mol (x 1/1)0.351 mol H2

↓[x24.8L·mol-1(SATP)]

8.70 L H2 @ SATPexpected

Get busy on this here work before I hog-tie y’all:

p 298 PP 1 – 10 (do a few)

p 300 PP 11 – 18 (do odd #s)

p 304 PP 21 – 30 (do odd #s)

p 305 RQ 4 – 10 (do as many as needed)

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