Calcium oxide reacts with water to produce calcium hydroxide and heat as shown by the equation.
CaO(s) + H2O(l) → Ca(OH)2(aq) + heat
When 32 g of CaO and 14 g of H2O react, how many grams of calcium hydroxide would you expect to be produced? Explain your answer.


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Respuesta :

Answer: The mass of [tex]Ca(OH)_2[/tex] produced is, 42.2 grams.

Explanation : Given,

Mass of [tex]CaO[/tex] = 32 g

Mass of [tex]H_2O[/tex] = 14 g

Molar mass of [tex]CaO[/tex] = 56 g/mol

Molar mass of [tex]H_2O[/tex] = 18 g/mol

First we have to calculate the moles of [tex]CaO[/tex] and [tex]H_2O[/tex].

[tex]\text{Moles of }CaO=\frac{\text{Given mass }CaO}{\text{Molar mass }CaO}[/tex]

[tex]\text{Moles of }CaO=\frac{32g}{56g/mol}=0.571mol[/tex]

and,

[tex]\text{Moles of }H_2O=\frac{\text{Given mass }H_2O}{\text{Molar mass }H_2O}[/tex]

[tex]\text{Moles of }H_2O=\frac{14g}{18g/mol}=0.777mol[/tex]

Now we have to calculate the limiting and excess reagent.

The balanced chemical equation is:

[tex]CaO(s)+H_2O(l)\rightarrow Ca(OH)_2(aq)+Heat[/tex]

From the balanced reaction we conclude that

As, 1 mole of [tex]CaO[/tex] react with 1 mole of [tex]H_2O[/tex]

So, 0.571 moles of [tex]CaO[/tex] react with 0.571 moles of [tex]H_2O[/tex]

From this we conclude that, [tex]H_2O[/tex] is an excess reagent because the given moles are greater than the required moles and [tex]CaO[/tex] is a limiting reagent and it limits the formation of product.

Now we have to calculate the moles of [tex]Ca(OH)_2[/tex]

From the reaction, we conclude that

As, 1 mole of [tex]CaO[/tex] react to give 1 mole of [tex]Ca(OH)_2[/tex]

So, 0.571 mole of [tex]CaO[/tex] react to give 0.571 mole of [tex]Ca(OH)_2[/tex]

Now we have to calculate the mass of [tex]Ca(OH)_2[/tex]

[tex]\text{ Mass of }Ca(OH)_2=\text{ Moles of }Ca(OH)_2\times \text{ Molar mass of }Ca(OH)_2[/tex]

Molar mass of [tex]Ca(OH)_2[/tex] = 74 g/mole

[tex]\text{ Mass of }Ca(OH)_2=(0.571moles)\times (74g/mole)=42.2g[/tex]

Therefore, the mass of [tex]Ca(OH)_2[/tex] produced is, 42.2 grams.