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
Please don't just tell me the answers, please explain as much as you can.
Thanks in advance :)
1- To find the total number of moles of CO used, we first need to determine the number of moles of Fe produced. From the balanced equation Fe2O3 + 3 CO = 2 Fe + 3 CO2, we can see that the stoichiometry between Fe2O3 and Fe is 2:2, meaning that for every 2 moles of Fe2O3, we have 2 moles of Fe. Therefore, 112 grams of Fe corresponds to 2 moles.
Next, we need to find the number of moles of CO used. According to the balanced equation, the stoichiometry between Fe2O3 and CO is 1:3. This means that for every 1 mole of Fe2O3, we need 3 moles of CO. Since we already know that we have 2 moles of Fe2O3, we can calculate the number of moles of CO required by multiplying 2 moles of Fe2O3 by 3 moles of CO per mole of Fe2O3, giving us a total of 6 moles of CO.
Therefore, the correct answer is (c) 3.0 moles of CO.
2- To find the number of moles of Al2O3 formed, we first need to determine the number of moles of Al used. From the balanced equation 4Al + 3O2 = 2Al2O3, we can see that the stoichiometry between Al and Al2O3 is 4:2, meaning that for every 4 moles of Al, we have 2 moles of Al2O3. Therefore, we need to calculate the number of moles of Al corresponding to 27 grams.
The molar mass of Al is 26.98 g/mol. To find the number of moles, we divide the given mass (27 grams) by the molar mass (26.98 g/mol):
27 g / 26.98 g/mol = 1.001 mol.
Therefore, we have approximately 1.001 moles of Al.
Since the stoichiometry between Al and Al2O3 is 4:2, we can say that for every 4 moles of Al, we have 2 moles of Al2O3. Therefore, since we have 1.001 moles of Al, the corresponding number of moles of Al2O3 will be (1.001 mol / 4 mol) * 2 mol = 0.5005 mol.
Therefore, the correct answer is (c) 0.50 moles of Al2O3.
3- Molarity is defined as the number of moles of solute (in this case NaOH) per liter of solution. To find the molarity, we need to determine the number of moles of NaOH and the volume of the solution.
The molar mass of NaOH is 22.99 g/mol + 16.00 g/mol + 1.01 g/mol = 39.99 g/mol. To find the number of moles, we divide the given mass (40 grams) by the molar mass (39.99 g/mol):
40 g / 39.99 g/mol = 1.001 mol.
Therefore, we have approximately 1.001 moles of NaOH.
The volume of the solution is given as 0.50 liters.
Now, we can find the molarity by dividing the number of moles of NaOH (solute) by the volume of the solution:
Molarity = 1.001 mol / 0.50 L = 2.002 M.
Therefore, the correct answer is (b) 2.0 M (rounded to the appropriate number of significant figures).
4- The freezing point of a solution is dependent on the concentration of dissolved particles, not the mass. According to the rules of colligative properties, the more solute particles present, the lower the freezing point of a solution.
The Van't Hoff factor (i) is the number of particles (ions, molecules) produced per formula unit of solute. For example, NaCl, which dissociates into Na+ and Cl- ions when dissolved in water, has an i value of 2, as it produces 2 particles.
In this case, we don't have the specific solute or its concentration, but we can assume it to be an electrolyte (a substance that dissociates into ions in water) for simplicity.
The number of dissolved particles is directly proportional to the number of moles of solute. This means that the solution with the highest freezing point would be the one with the lowest concentration (fewer particles).
Since all options have the same molar mass (1 kg), we need to determine which option has the fewest dissolved particles.
The option with 1 x 10^17 dissolved particles would have the highest freezing point because it has the lowest concentration of dissolved particles. Therefore, the correct answer is (d) 1 x 10^17 dissolved particles.
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).
Check my work. Check my thinking
Please don't just tell me the answers, please explain as much as you can.
Thanks in advance :)
In the future, tell us how you would work the problem. Most of us will gladly CHECK your answers (that's fairly fast for us) but few will provide detailed work to let YOU check yours (it takes us MUCH longer to do that.)