Question

Elemental potassium reacts violently with water. The reactionusually results in a lilac-colored flame, fueled by the formation offlammable hydrogen gas, as seen in the reaction below. How manygrams of hydrogen are produced when 43.7 grams of potassiumare tossed into water? Show all work and give your answers tothree significant figures.2K + 2H2O -> 2KOH + H2M(K) = 39.10 g/mol; M(H2O) = 18.01 g/mol; M(KOH) = 56.11 g/mol;M(H2) = 2.02 g/mol

Answer 1

Explanation:

First, we need to rewrite the equation:

2K + 2H2O -> 2KOH + H2

This equation tells us that 2 moles of K react with 2 moles of H2O and produce 2 moles of KOH and 1 mole of H2.

If we have 43.7 grams of potassium, we can transform it into moles, compare with the ratio between Potassium and Hydrogen (H2) and then, calculate the quantity of hydrogen in grams.

So first, let's transform 43.7 grams of K into moles using the following formula:

moles = mass/molar mass

molar mass of K = 39.10 g/mol

moles = 43.7/39.10

moles = 1.12 moles

So:

2 moles of K --- 1 moles of H2

1.12 moles of K --- x moles of H2

2x = 1.12

x = 1.12/2

x = 0.559 moles of H2

Now let's transform moles into grams using the following formula:

mass = moles x molar mass

molar mass of H2 = 2.02 g/mol

mass = 0.559 x 2.02

mass = 1.13 g

Answer: It is produced 1.13 grams of H2.