Design a device that will knock a block of wood a distance of 5 meters.

That was the challenge in science class. Ben and Sam designed a pendulum to move the wood block. Their first design moved the block about 1.5 meters. They rebuilt their pendulum and changed the mass of the pendulum bob. After they made several changes in the mass of the bob, they finally knocked the wooden block 7.0 meters.
Each time Ben and Sam tried a new mass for the pendulum bob they were
A) designing a product.
B) identifying a problem.
C) evaluating the design.
D) implementing the design.

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.

wher is the rest of the question