# Chemistry (Regents level)

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1- In the reaction Fe2O3 + 3 CO = 2 Fe + 3 CO2, what is the total number of moles of CO used to produce 112 grams of iron?
a) 1.0 b)2.0 c)3.0 d)4.0

2- Given the reaction:
4Al + 3O2 = 2Al2O3
How many moles of Al2O3 will be formed when 27 grams of Al reacts completely with O2?
a) 1.0 b)2.0 c)0.50 d)4.0

3- What is the molarity of a solution that contains 40 grams of NaOH in 0.50 liter of solution?
a) 1.0M b)2.0M c)0.25M d)0.50M

4- A 1-kilogram sample of water will have the highest freezing point when it contains
a) 1 x 10^23 dissolved particles
b) 1 x 10^21 dissolved particles
c) 1 x 10^19 dissolved particles
d) 1 x 10^17 dissolved particles

• Chemistry (Regents level) -

1- In the reaction Fe2O3 + 3 CO = 2 Fe + 3 CO2, what is the total number of moles of CO used to produce 112 grams of iron?
a) 1.0 b)2.0 c)3.0 d)4.0

Convert 112 g Fe to mols. mols = grams/atomic mass. 112/55.85 = 2.00
Look at the equation. 2 mol Fe are produced for every 3 mols CO; therefore, the answer is 3.0.

2- Given the reaction:
4Al + 3O2 = 2Al2O3
How many moles of Al2O3 will be formed when 27 grams of Al reacts completely with O2?
a) 1.0 b)2.0 c)0.50 d)4.0

Convert 27 g Al to mols.
Convert mols Al to mols Al2O3 using the coefficients in the balanced equation.
27 g Al x (1 mol Al/27 g Al) = 1 mol Al.
1 mol Al x (2 mols Al2O3/4 mol Al) = ??

3- What is the molarity of a solution that contains 40 grams of NaOH in 0.50 liter of solution?

molarity = mols/L
mols = g/molar mass
molar mass NaOH = 40
mol NaOH = 40g NaOH/40 = 1 mol
molarity = mols/L = 1 mol/0.50 L = ??

a) 1.0M b)2.0M c)0.25M d)0.50M

4- A 1-kilogram sample of water will have the highest freezing point when it contains
a) 1 x 10^23 dissolved particles
b) 1 x 10^21 dissolved particles
c) 1 x 10^19 dissolved particles
d) 1 x 10^17 dissolved particles

delta T = Kb*m*i
delta T is change in freezing point (from zero Celsius).
Kb is constant.
m = molality of solution
i = number of particles
The largest number will provide the largest number of particles and that will provide the largest delta T (which will be the lowest freezing point). Therefore, the highest freezing point must be from the solution containing the fewest particles and that appears to be answer (d).

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• Chemistry (Regents level) -

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