Which of the following is true regarding the concentration of solutions?
a. percent solutions are parts per 1000 parts.
b. molarity is one mole of solute per 1000 ml of solution.
c. to calculate molarity, one must know the atomic weight of the solvent.
d. to calculate molarity, one must know the atomic number of the solute

The correct answer is Option B.

Explanation:

Percent solution by mass (% m/m) means that amount of solute present in 100 grams of solution.

Percent solution by volume (% m/v) means that amount of solute present in 100 mL of solution.

Molarity is defined as the number of moles of solute present in 1 L of solution or 1000 mL of solution.

Hence, the correct answer is Option B.

first, consult an activity series chart to determine if al is more reactive than fe. it is, so it will replace the fe. now, one can continue with the problem.

next, make sure you have a correctly balanced equation.

3feo + 2al ==> 3fe + al2o3

now, determine which reactant (feo or al) is in limiting supply.

moles feo present = 125 g x 1 mole/71.8 g = 1.74 moles

moles al present = 25.0 g x 1 mole/26.98 g = 0.927 moles

since from the balanced equation, it take 3 mol feo for every 2 mol al, al will be limiting.

you can determine this simply by dividing moles of each by their coefficient in the balanced equation. for example: 1.74/3 = 0.58 and 0.927/2 = 0.464. al is less, so it is limiting.

finally, using the stoichiometry in the balanced eq. determine mass of fe that can be produced from 0.927 moles of al.

0.927 moles al x 3 moles fe/2 moles al x 55.8 g/mole = 77.6 g