AP Chemistry Question of the Day --44

Welcome back to my blog. Here comes the answer to question 43 I posted earlier. The correct answer is C. 

The potential energy of the products are higher than that of the reactants. The forward reaction is endothermic. When temperature is increased, the forward reaction is favoured and the equilibrium shifts to the right.

Activation energy for any reaction is positive. It is defined as the minimum energy required for a effective collision to happen. A is not correct.

Starting with reactants only, the forward reaction rate will decrease with the decrease in reactant concentration and the backward reaction rate will increase with the concentrate of the product increasing. When both rate are equal, the reaction reaches equilibrium. B is not right.

The potential energy of the products are higher than that of the reactants. The activation energy for the forward reaction is higher than that of the reverse reaction. D is not right.

The potential energy of the products are higher than that of the reactants. The forward reaction is endothermic. The enthalpy change for the forward reaction is positive. E is incorrect.

Following is Question 44 of the series. 

44. Suppose that conversion of reactant R to product P involves the following sequence of reversible reactions. When the system reaches a state of dynamic equilibrium, which of the following statements is true? 

A The rate of step R → Q is equal to the rate of step Q → P. 
B [R] = [Q] = [P] 
C [Q] = [P] / [R] 
D The rate of step Q → R is equal to the rate of step Q → P. 
E The rate of step R → Q is equal to the rate of step Q → R. 

I will post the answer and explanation tomorrow. 

Thank you very much for reading my post, I am available to discuss any topics in AP chemistry. Please give me a call at 604-808-6827 or email me at vancouverchemistrytutor@gmail.com. My website is located at www.vancouverchemistrytutor.com.

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AP Chemistry Question of the Day --43

Welcome back to my blog. Here comes the answer to question 42 I posted earlier. The correct answer is D. 

Ionic compounds are mostly formed between a metal and a non metal. The only exception is ammonium salt where NH4 is a polyatomic ion. It has covalent bond inside the ammonium ion and the bond between ammonium and the anion is ionic.
D is the only compound that is not ionic.

Following is Question 43 of the series. 

43. Consider the following energy level diagram for a reaction that occurs in a single step. Which of the following statements is true? 

A The activation energy for the reverse reaction is less than zero. 
B Starting from reactants only, and before equilibrium is established, the rate of the forward reaction continually increases. 
C The effect of a temperature change on the rate is greater for the forward reaction than for the reverse reaction. 
D The activation energy for the forward reaction is less than that of the reverse reaction. 
E The enthalpy change for the forward reaction is less than zero. 

I will post the answer and explanation tomorrow. 

Thank you very much for reading my post, I am available to discuss any topics in AP chemistry. Please give me a call at 604-808-6827 or email me at vancouverchemistrytutor@gmail.com. My website is located at www.vancouverchemistrytutor.com.

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AP Chemistry Question of the Day --42

Welcome back to my blog. Sorry for the delay updating my blog. My computer had some problems. Here comes the answer to question 41 I posted earlier. The correct answer is A. 

Since the system is assumed thermally insulated from the surroundings, according to the First Law of Thermodynamics, energy can not be produced or consumed and only can  be transferred. The heat water absorbed should be equal to the heat the metal lost.

Following is Question 42 of the series. 

42. Which of the following is not an ionic compound? 

A ammonium fluoride, NH4F 
B sodium hydroxide, NaOH 
C lithium nitrate, LiNO3 
D oxygen difluoride, OF2 
E potassium hydride, KH 

I will post the answer and explanation tomorrow. 

Thank you very much for reading my post, I am available to discuss any topics in AP chemistry. Please give me a call at 604-808-6827 or email me at vancouverchemistrytutor@gmail.com. My website is located at www.vancouverchemistrytutor.com.

Regards!

AP Chemistry Question of the Day --41

Welcome back to my blog. Here comes the answer to question 40 I posted yesterday. The correct answer is C. 

Assume we have 100g of the sample, then we will have 48.5g oxygen and 51.5g vanadium. 

V and O has a 1:3 ratio. As a result, the empirical formula of the oxide is VO3.

Following is Question 41 of the series. 

41. When 0.100 kg of solid metal at 95.0 °C is placed into 0.300 kg of water at 25.0 °C, the final temperature of the system is 27.4 °C. What is the identity of the metal? Assume the system is thermally insulated from its surroundings. 

A Fe(s) 
B Sn(s) 
C Mn(s) 
D Ti(s) 
E Pb(s) 

I will post the answer and explanation tomorrow. 

Thank you very much for reading my post, I am available to discuss any topics in AP chemistry. Please give me a call at 604-808-6827 or email me at vancouverchemistrytutor@gmail.com. My website is located at www.vancouverchemistrytutor.com.

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AP Chemistry Question of the Day --40

Welcome back to my blog. Here comes the answer to question 38 I posted yesterday. The correct answer is C. 

First let's refresh our minds with the rules of writing Lewis structures.

1. —Determine the central and terminal atoms

2. Determine the total valence electrons in molecule or ion

—3. Form single bond between atoms.

—4. Any electrons remaining are placed on terminal atoms first to meet octet rule.

—5. Form double or triple bond if the central atom has less than eight electrons. If B is the central atom, it can have less than 8 electrons. —The central atom may have more than 8 electrons only if it is in period 3-7. The max. number of electrons is 12.

From the question, it is stated that S is the central atom. The total numbers of valence electrons are 6+6+7+7=26. 6 are used to make the S-O and 2S-Cl bonds. 18 will be used to make all the terminal atoms octet. The two electrons that are left over are then placed on the central S atom. Now we count the number of electron groups around S which is 4. So The central S takes tetrahedron geometry and the bond angle would be close to 109. C is the correct answer. 

Following is the Lewis structure for SOCl2:

Following is Question 40 of the series. 

40. 

I will post the answer and explanation tomorrow. 

Thank you very much for reading my post, I am available to discuss any topics in AP chemistry. Please give me a call at 604-808-6827 or email me at vancouverchemistrytutor@gmail.com. My website is located at www.vancouverchemistrytutor.com.

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AP Chemistry Question of the Day --39

Welcome back to my blog. Here comes the answer to question 38 I posted yesterday. The correct answer is B. 

Following is Question 39 of the series. 

39. 

I will post the answer and explanation tomorrow. 

Thank you very much for reading my post, I am available to discuss any topics in AP chemistry. Please give me a call at 604-808-6827 or email me at vancouverchemistrytutor@gmail.com. My website is located at www.vancouverchemistrytutor.com.

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AP Chemistry Question of the Day --38

Welcome back to my blog. Here comes the answer to question 37 I posted yesterday. The correct answer is D. 

When writing net ionic reactions, the following needs to be kept in mind:
1. If the substance is a strong electrolyte, it dissociates in water completely. We write them as dissociated ions. All soluble ionic compounds are strong electrolyte. Although HCl, HBr and HI are covalent compounds, they are strong acid and dissociate completely in water as well. 
2. If the substance is a weak electrolyte, it barely dissociate in water and we write it in its molecular form. All covalent compounds except HCl, HBr and HI are weak electrolyte, including water itself.
3. If the substance is a salt but is not soluble in water, we write it in molecular form too because it is mainly staying in the solid state as a solid.
4. If an ion is on both side of the equation, it is called a spectator ion and it should be cancelled out and not appear in the final net ionic equation. 

Now we look at our question. HClO is a weak acid as stated in the question. Ca(OH)2 is a strong electrolyte. the product Ca(ClO)2 is also a strong electrolyte. Water is a weak electrolyte. As a result the reaction can be written as:

Calcium ion appears on both sides of the equation, we cancel it out and the final net ionic reaction is:

This is answer D.

Following is Question 38 of the series. 

38. 

I will post the answer and explanation tomorrow. 

Thank you very much for reading my post, I am available to discuss any topics in AP chemistry. Please give me a call at 604-808-6827 or email me at vancouverchemistrytutor@gmail.com. My website is located at www.vancouverchemistrytutor.com.

Regards!