IIT/JEE Chemistry Practice #11: Moles/Molarity

Dave explains concepts of moles and molarity through two questions. The first involves calculating the concentration of a resulting solution from mixing two solutions. The second question focuses on determining the moles of magnesium phosphate containing a specific number of oxygen atoms. Key steps include understanding molarity, calculating moles, and using molecular formulas.

What is the first step in finding the concentration of a resulting solution when two solutions are mixed?

• Find the density of the solutions.

• Measure the temperature of the solutions.

• Determine the moles in each individual solution.

• Calculate the total volume of the solutions.

How do you calculate the total moles in a mixed solution?

• Add the molarity of both solutions.

• Multiply the volume by the molarity for each solution and sum the results.

• Divide the total volume by the molarity.

• Subtract the smaller molarity from the larger one.

What is the concentration of the resulting solution when 400 mL of 1.5 M solution is mixed with 520 mL of 1.2 M solution?

• 1.50 M

• 1.45 M

• 1.25 M

• 1.34 M

What is the molecular formula for magnesium phosphate?

• MgPO4

• Mg2(PO4)3

• Mg(PO4)2

• Mg3(PO4)2

How many moles of magnesium phosphate contain 0.25 moles of oxygen atoms?

• 0.031 moles

• 0.25 moles

• 0.062 moles

• 0.125 moles