Answer :
Answer : Option A , 33.7 moles
Solution:
We are given :
• Mass of Ca(OH)2 = 2.5 kg = 2.5kg *1000g/kg = ,2500 grams,.
Step 1:
Calculate Molecular Mass of Ca(OH)2 = 74.09268 mol/g, calculated as follows :
[tex]\begin{gathered} \text{Mol mass Ca(OH2 ) = mol mass Ca + 2}\cdot mol\text{ mass O + 2 }\cdot\text{ mol mass H } \\ \text{=40.098 + 2}\cdot15.999\text{+ 2 }\cdot1.00784 \\ =74.093\text{ g/mol} \end{gathered}[/tex]Recall that Molecular mass of a substance is obtained from the periodic table .
Step 2 : Use the formula : moles = mass /molecular mass , to calculate number of moles of Ca(OH)2:
[tex]\begin{gathered} \text{Moles Ca(OH)}_2=\text{ }\frac{massCa(OH)_2}{lecularmassCa(OH)_2} \\ \text{ =}\frac{2500\text{ g }}{74.093g}\cdot\text{ mol } \\ \text{ =33.74 moles } \\ \text{ }\approx33.7\text{ moles } \end{gathered}[/tex]