PAY 2 - 5th Grade Science STAAR Review Matter and Energy Readiness TEKS 5.5A
4. Enrique mixes yellow pellets in water. After stirring the
yellow pellets around in the water, they begin to disappear
Later, Enrique heats the mixture until all the water is
evaporated, and a yellow powder is at the bottom of the
beaker. What physical property of the yellow substance ha
Enrique demonstrated?
F. Density
6. Magnetism
H. Solubility
J. Mass
5. What physical property of foam makes it a good
use in life vests?

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.

a small container that holds a source of energy a solar cell that captures light energy and converts it into electricity a voltaic cell that uses the oxidation of a fuel to produce electricity

explanation:

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