Consider the following data for five hypothetical elements: Q, W, X, Y, and Z. Rank the elements from most reactive to least reactive. Combination Observation of reaction Q W Reaction occurs X Z No reaction W Z Reaction occurs Q Y Reaction occurs Place the element symbols from most to least reactive. Combination Observation of reaction
Q + w+ Reaction occurs
x +z+ No reaction
w + z+ Reaction occurs
Q+ + Y Reaction occurs

Y, Q, W, Z and X

Y > Q > W > Z > X

Explanation:

To know the most reactive element, the element will be able to displace other metal in it compound. We also have to observe if the reaction occur. If the reaction didn't occur, that means the element is not reactive than the metal found in the other reactant. Invariably their will be no displacement.

Q + w+ Reaction occurs

Q element displace the metal w in it compound . This means Q is more reactive.

x +z+ No reaction

No reaction here. This means x is less reactive than z as it couldn't displace z in it compound.

w + z+ Reaction occurs

w is more reactive than z as it displaces z in it compound.

Q+ + Y Reaction occurs

Y is more reactive than Q as it displaces Q in it compounds.

Therefore, the most reactive to the least reactive is arrange as follows.

Y, Q, W, Z and X

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.