The law of conservation of energy states that
1) The law of conservation of energy states that ________.
A) the energy of the reactants and products in a chemical reaction are always equal
B) all chemical reactions are reversible
C) energy can be created, but not destroyed
D) energy cannot be created or destroyed
2) Which of the following energy quantities is equivalent to 578 J?
A) 5.78 × 105 kJ C) 0.138 kcal
B) 138 kcal D) 1.38 × 105 kcal
3) Which of the following energy quantities is equivalent to 11.9 kcal?
A) 1.19 × 105cal C) 49.8 kJ
B) 49.8 J D) 2.84 × 103 kJ
4) Which of the following energy quantities is equivalent to 258 Cal?
A) 258 cal C) 1080 kJ
B) 1080 J D) 6.17 × 104 kJ
5) Which quantity represents the largest amount of stored energy?
A) 10 grams of fat
B) 10 grams of carbohydrate
C) 10 grams of protein
D) 5 grams of carbohydrate plus 5 grams of protein
E) 5 grams of protein plus 5 grams of fat
6) Which bond is the strongest?
A) H–Br C) H–F
B) H–Cl D) H–I
7) Which bond is the weakest?
A) H–Br C) H–F
B) H–Cl D) H–I
8) Which term correctly describes a reaction in which the energy of the products is higher than the energy of the reactants?
A) Oxidation-reduction C) Exothermic
B) Endothermic D) Combustion
9) Consider the reaction: C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g), where ΔH = –531 kcal. Which statement concerning this reaction is true?
A) Heat is absorbed.
B) The bonds formed in the products are stronger than the bonds broken in the reactants.
C) The products are higher in energy than the reactants.
D) The reaction is endothermic.
Short Answer / Problem Solving (Show your work):
10) A chemical reaction requires 31.39 kJ. How many kilocalories does this correspond to?
11) A peanut butter and jelly sandwich contains 9.00 g of fat, 6.00 g of protein, and 25.0 g of carbohydrate. How many Calories does this sandwich provide?
12) Consider the reaction, C2H4(g) + H2(g) → C2H6(g), where ΔH = –137 kJ. How many kilojoules are released when 3.5 mol of C2H4 reacts?
13) Consider the reaction, C2H4(g) + H2(g) → C2H6(g), where ΔH = –137 kJ. How many kilojoules are released when 55.3 g of C2H4 reacts?
14) Watch the following video and complete the calculation to determine the specific heat of the cadmium metal: https://www.youtube.com/watch?v=8gHFaL2990U
Week 6 Assignment – Part B
Multiple Choice:
1) An equilibrium constant with a value of 8.0 × 106 indicates that at equilibrium ________.
A) the reactants are favored
B) the products are favored
C) approximately equal concentrations of reactants and products are present
D) there are more reactants present than products
2) Which K value below is consistent with an equilibrium system in which the reactants are favored?
A) K = 1
B) K = 1.8 x 103
C) K = 3.7 x 10–8
D) K = 500
3) Which statement about catalysts is NOT true?
A) A catalyst increases the rate of a chemical reaction.
B) A catalyst lowers the activation energy of a chemical reaction.
C) A catalyst lowers the ΔH of a chemical reaction.
D) A catalyst is recovered unchanged in the reaction it catalyzes.
4) Which of the following is ALWAYS necessary for a chemical reaction to occur between two reactants, A and B?
A) Equal amounts of A and B must be present
B) A and B must be present in the same physical state
C) The reaction must be carried out at a temperature higher than room temperature
D) A and B must collide with the proper orientation and with a certain minimum amount of energy
In each of the following questions, identify which way (to the left or to the right) does equilibrium shift to relieve the described applied stress:
5) Consider the following reversible reaction at equilibrium: CO(g) + Cl2(g) ? COCl2(g). If chlorine gas is added to the equilibrium system, how is the stress relieved
6) Consider the following reversible reaction at equilibrium: C6H12O6 (aq) + 6 O2(g) ? 6 CO2(g) + 6 H2O(l). If oxygen gas is removed from the equilibrium reaction vessel, how is the stress relieved?
7) Consider the following reversible reaction at equilibrium: C6H12O6 (aq) + 6 O2(g) ? 6 CO2(g) + 6 H2O(l). Given that this reaction is exothermic, if heat is added to the equilibrium system, how is the stress relieved?
8) Label each identified lettered component of the energy diagram for the arbitrary chemical reaction below:
Problem Solving (Show your work):
9) What is the symbolic expression for the equilibrium constant for the reaction:
2 C2H6(g) + 7 O2(g) ? 4 CO2(g) + 6 H2O(g)?
10) What is the gas phase chemical reaction that corresponds to the equilibrium constant expression shown below?
11) Consider the reaction: N2(g) + O2(g) ? 2 NO(g). If [N2] = 0.520 M, [O2] = 0.0662 M, and [NO] = 0.00956 at equilibrium, calculate the value of K and describe the physical/chemical interpretation of this K value.
K=(0.00956)^2/(0.520)(0.0662)
K=9.139X10^-5/0.03442
12) Watch the following video that illustrates a series of experimentsthat demonstrate Le Chatelier’s principle:https://www.youtube.com/watch?v=ZOYyCTvLa9E
In this video, you will observe several examples of external stresses that act upon the equilibrium chemical reaction:
Fe_aq^(+3)+SCN_aq^(-1)?Fe(SCN)_aq^(+2)
Each stress will serve to either add or remove reactant or product.
A) Describe what happens when iron nitrate or potassium thiocyanate (reactant) are added to the control tube? Describe your observation in the context of Le Chatelier’s principle.
B) Describe what happened when sodium hydroxide was added to the control tube? Does the addition of sodium hydroxide add or remove a reactant or product? If so, clearly state the effect of adding sodium hydroxide and how equilibrium shifts to relieve this stress.
C) Similarly, describe what happened when potassium chloride was added to the control tube?
D) Next, describe what happened when silver nitrate was added to the control tube?
E) Lastly, describe what happens when Mercury (II) Nitrate was added to the control tube?
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