Question

Assume that the chemical reaction shown started out having a total of 15g of potassium and water How much potassium hydroxide and hydrogen gas will be produced by the chemical reaction? Show your work

Answer 1

Given :

15 g of potassium react with water .

To Find :

How much potassium hydroxide and hydrogen gas will be produced by the chemical reaction .

Solution :

Balanced chemical equation is given by :

$2K+2H_2O->2KOH+H_2$

Number of moles of potassium are :

$n_p=\dfrac{15}{39}\ mole\\\\n_p=0.38\ mole$

From the chemical equation we can see that 1 mole of potassium produce 2 moles of KOH and 1 mole $H_2$ .

So , 0.38 mole of potassium will produce :

$n_{KOH}=2\times 0.38\\\\n_{KOH}=0.76\ moles$

$n_{H_2}=0.38\ mole$

Mass of KOH produced , $0.76\times 56\ g=42.56\ g$ .

Mass of $H_2$ produced , $0.38\times 2=0.76\ g$ .

Therefore , mass of potassium hydroxide and hydrogen gas produced is 42.56 g and 0.76 g respectively .

Answer 2

The mass of KOH and H2 are 21.56 grams and 0.386grams

Given the balanced chemical reaction between potassium and water is given as;

• $2K+2H_2O\rightarrow 2KOH + H_2$

Get the number of moles of potassium.

• Moles  = Mass/molar mass

• Moles = 15/39

• Moles =  0.385 moles

Based on stochiometry, 2 moles of potassium produces 2 mols of KOH and 1 mole of hydrogen gas.

Number of moles of KOH  = 0.38 moles

Number of moles of H2 = 0.385/2 = 0.193 moles

Get the mass of KOH

• Mass of KOH = moles of KOH * molar mass of KOH

• Mass of KOH = 0.385 * 56

• Mass of KOH = 21.56 grams

Get the mass of hydrogen

• Mass of H2 = moles of H2 * molar mass of H2

• Mass of H2 = 0.193 moles * 2

• Mass of H2 = 0.386grams

Hence the mass of KOH and H2 are 21.56 grams and 0.386grams

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