AP Chemistry Question of the Day --37

Welcome back to my blog. Here comes the answer to question 36 I posted yesterday. The correct answer is D. 

When writing ground state electronic configurations, we have to follow several rules:
1. Aufbau Principle: Electrons fill the lowest energy orbitals first.  The order of energy level is: 1s 2s 2p 3s 3p 4s 3d 4p 5s 3d 5p 6s 4f 5d 6p 7s 5f 6d 7p .....
2. Pauli Exclusion Principle:  In a given atom, no two electrons can have the same set of 4 quantum number. This rule determined that each orbital can hold only two electrons.
3. Hund Rule: —The lowest energy state of an atom is the one having the max numbers of unpaired electrons. When electrons are filling degenerate orbitals, they tend to occupy all the orbitals first and then pair up if they have to.

No    Now we see, The electron configuration of the atoms are:

         

According to the Hund Rule, if a sublevel is not fully filled, electrons tend to occupy all the orbitals with the same energy level first and then pair up if necessary. Li has 1, B has 1, Sc has 1, V has 3 and Ni has 2 unpaired electrons respectively.

Following is Question 37 of the series. 

37. What is the net ionic equation for the reaction that occurs when aqueous solutions of HOCl, a weak acid, and calcium hydroxide, Ca(OH)2, are combined? 

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 --36

Welcome back to my blog. Here comes the answer to question 35 I posted yesterday. The correct answer is C. 


The above reaction can be the sum of the following two reactions:

So, C is the correct answer.

Following is Question 36 of the series. 

36. Which of the following has three unpaired electrons in its lowest energy state? 

A Li 

B B 

C Sc 

D V 

E Ni 

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 --35

Welcome back to my blog. Here comes the answer to question 34 I posted on Friday. The correct answer is A. 

Adding something that reacts with Co2+(aq) would decrease the concentration of Co2+ and hence shift the equilibrium toward the right to offset the disturbance.

Since the reaction is exothermic, increasing the temperature of the reaction will shift the equilibrium to 
the left.

Adding a fluoride salt will increase the concentration of fluoride, which is a product of the reaction and will shift the equilibrium to the left.

Adding a catalyst will not shift the equilibrium. Catalyst can only make it faster to reach equilibrium.

Decreasing the volume of the reaction will shift the equilibrium towards the direction where less gas molecules are. In this case, it is shifting to the left.

So, A is the correct answer.

Following is Question 35 of the series. 

35. Given the following reactions and equilibrium constants:

what is K for the reaction shown below? 

 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 --34

Welcome back to my blog. Here comes the answer to question 33 I posted yesterday. The correct answer is B. 

Following is Question 34 of the series. 

34. The following exothermic reaction reaches equilibrium in a closed reaction vessel, 

Which of the following actions causes net reaction from left to right? 
A adding something that reacts with Co2+(aq) 
B increasing the temperature 
C adding some soluble fluoride salt, such as NaF(s) 
D adding a catalyst 
E decreasing the volume of the reaction vessel 

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 -33

Welcome back to my blog. Here comes the answer to question 32 I posted yesterday. The correct answer is B. 

The sum of oxidation numbers of the individual element should be equal to the total charge of the particle. Since all the available choices are neutral, the sum of oxidation number should be zero. K always has +1 oxidation state in its compounds. Oxygen normally has an oxidation state of -2 except in peroxide compounds where its oxidation state is -1. Halogens always has oxidation state of -1.

Thus, Mn's oxidation states are +4, +2, +6, +7 and +7 in the five choices.  Answer B has the lowest.


Following is Question 33 of the series. 

33. How many moles of K+ ions are there in 0.12 L of 0.015M  K2SO4(aq)? 

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 --32

Welcome back to my blog. Here comes the answer to question 31 I posted yesterday. The correct answer is E.

When pressure is high and temperature is low, we can consider gases as ideal gas and they obey the ideal gas law. The molar volume of any gas would be the same at the same pressure and temperature according to PV=nRT, the molar volume (n=1)would be: V(molar)=RT/P. Under ideal gas conditions, the volume and the intermolecular interactions between gas molecules are negligible. However, when temperature is low and the pressure is high, especially when the gas is close to condense, both the volume and the intermolecular forces have to be taken into account. The stronger the intermolecular force, the less the volume. Both C2H6  and H2 are non polar molecules. Since C2H6 has higher molecular weight and more complicated electronic structure, it has stronger London Dispersion forces than H2. So E is the right answer.

Answer A is incorrect because C2H6 is larger than H2. The average kinetic energy is only dependent on the temperature. At the same temperature,  both gases have the same average kinetic energy. Thus, B and C are wrong. 



Following is Question 32 of the series. 

32. In which compound does manganese have the lowest oxidation state? 

A MnO2 
B MnI2 
C K2MnO4 
D Mn2O7 
E KMnO4 

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 --31

Welcome back to my blog. Here comes the answer to question 30 I posted yesterday. The correct answer is C. 

Water is a very polar molecule while hydrocarbons of high molecular weight are unpolar compounds. According to "Like dissolves like" Rule, The solubility of high molecular hydrocarbons will be very low in water.
Due to hydrogen bonding, water has a higher density as a liquid than as a solid, because the lattice structure in ice restricted the number of hydrogen bonding while in liquid water, the maximum hydrogen bonding could be achieved. Thus A and B are correct. Answer D is also correct because when we write the Lewis structure of water, the central oxygen atom has two bonds connected to hydrogen and two lone pairs of electrons. The central oxygen atom is sp3 hybridized and takes tetrahedron geometry. As the two lone pair electrons are not visible, the molecule appears as a bent shape.

Following is Question 31 of the series. 

31. Which of the following statements accounts for the observation that, at 300 K and 10 atm, the molar volume of C2H6(g) is less than that of H2(g)? 

A C2H6 molecules are smaller than H2 molecules. 
B The average kinetic energy of H2 molecules is greater than that of C2H6 molecules. 
C The average kinetic energy of H2 molecules is less than that of C2H6 molecules. 
D The intermolecular attractions in C2H6(g) are weaker than they are in H2(g). 
E The intermolecular attractions in C2H6(g) are stronger than they are in H2(g). 

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!