Answer:
92.9%
Explanation:
You have been given the actual yield of the reaction. First, you need to find the theoretical yield of the reaction. To do this, you need to (1) convert grams Fe₂O₃ to moles Fe₂O₃ (via molar mass from periodic table values), then (2) convert moles Fe₂O₃ to moles Fe (via mole-to-mole ratio from reaction coefficients), and then (3) convert moles Fe to grams Fe (via molar mass).
Once you have found the theoretical yield, you need to use the percent yield equation to calculate the final answer. This number should have 3 sig figs to match the given values.
<u>(Step 1)</u>
Molar Mass (Fe₂O₃): 2(55.845 g/mol) + 3(15.998 g/mol)
Molar Mass (Fe₂O₃): 159.684 g/mol
1 Fe₂O₃(s) + 3 CO(g) ---> 2 Fe(s) + 3 CO₂(g)
Molar Mass (Fe): 55.845 g/mol
50.0 g Fe₂O₃ 1 mole 2 moles Fe 55.845 g
-------------------- x ------------------ x --------------------- x ---------------- = 35.0 g Fe
159.684 g 1 mole Fe₂O₃ 1 mole
<u>(Step 2)</u>
Actual Yield
Percent Yield = --------------------------- x 100%
Theoretical Yield
32.5 g Fe
Percent Yield = ---------------------- x 100% = 92.9%
35.0 g Fe
Answer: m= 0.69 m or mol/kg
Explanation: Molality is expressed as moles per unit kilograms of solvent or m= n / kg
First convert 25.0 g NaCl to moles
25.0 g NaCl x 1 mole NaCl / 58 g NaCl
= 0.43 moles NaCl
Next convert 625 g H2O to kilograms
625 g H2O x 1 kg / 1000 g H2O
= 0.625 kg H2O
Substitute the values in the formula
m = n / kg
= 0.43 mole NaCl / 0.625 kg
= 0.69 m or mole / kg
Answer:
Explanation:
The total energy or intrinsic energy of a system is called the enthalpy. In thermochemistry, we have two types of enthalpy changes which are:
- Exothermic changes
- Endothermic changes
For the freezing of water, the enthalpy change is an exothermic one. Exothermic changes are designated as negative. In this chemical change, heat is liberated to the surroundings and this leaves the environment at a much higher temperature. In freezing, the enviroment gains more heat as the material begins to cool to lower temperature.
Entropy is the degree of randomness or disorderliness of a system. When a phase change occurs from liquid to solid, freezing takes place. Such a change increases the orderliness of a system and entropy diminishes. Here, entropy is negative.
The free energy is a measure of the energy a system that does useful work. Free energy depends on enthalpy, entropy and temperature of a system. For phase changes such as freezing of water, the value of free energy change is 0.
For this process, an increases in temperature makes it non-spontaneous. Increasing temperature would alter the course of the reaction and makes it exothermic. For entropy, increasing temperature would increase entropy and therefore, the reaction would not be feasible.
Temperature would mostly affect the free energy. An increase in temperature would increase the value of entropy change and the reaction would not be spontaneous. With falling temperature value, the reaction becomes more spontaneous and favored.
Answer:
Option a.
0.01 mol of CaCl₂ will have the greatest effect on the colligative properties, because it has the biggest i
Explanation:
To determine which of the solute is going to have a greatest effect on colligative properties we have to consider the Van't Hoff factor (i)
These are the colligative properties:
ΔP = P° . Xm . i → Lowering vapor pressure
ΔT = Kb . m . i → Boiling point elevation
ΔT = Kf . m . i → Freezing point depression
π = M . R . T → Osmotic pressure
Van't Hoff factor are the numbers of ions dissolved in the solution. For nonelectrolytes, the i values 1.
CaCl₂ and KNO₃ are two ionic solutes. They dissociate as this:
CaCl₂ → Ca²⁺ + 2Cl⁻
We have 1 mol of Ca²⁺ and 2 chlorides, so 3 moles of ions → i = 3
KNO₃ → K⁺ + NO₃⁻
We have 1 mol of K⁺ and 1 mol of nitrate, so 2 moles of ions → i = 2
Option a, is the best.
