July 31, 2017

In solid methane, the forces between the neighboring CH4 molecules are best characterized as 

a. ionic 

b. covalent

c. hydrogen

d. ion-ion

e. London (dispersion) forces

Answer and Explanation:

In order for us to identify the type of correct intermolecular forces, we need to first identify what kind of molecule CH4 is. 

Ionic forces are present in ionic compounds. Ionic compounds have a metal with a nonmetal or a metal with...

July 28, 2017

According to sciencedaily.com, a new study found that both healthy adults and those experiencing mental health conditions who participate in arts-based groups such as creative writing or choir benefit greatly benefit from them. Those who participate in these groups reported a significant increase in positive emotions and a significant decrease  in negative emotions. 

Adults with chronic mental health conditions were...

July 25, 2017

Which substance has nonpolar covalent bonds?

(1) Cl2

(2) SO3

(3) SiO2 

(4) CCl4

Answer and Explanation: Covalent bonds are formed between 2 or more nonmetals. Looking at the answer choices, we can see that all of the answers have nonmetals, and therefore all have covalent bonds. The molecule that is composed of the same 2 elements has non polar covalent bonds since if the elements are the same they have the same electronega...

July 23, 2017

Physics plays a relatively minor role in the new MCAT. In fact, only one quarter of the questions on the Chemistry/Physics section actually test general physics knowledge. From my experience teaching MCAT physics, many mistakes people make on this section of the exam are due to errors in mathematical reasoning rather than physics content knowledge. Two common mistakes include:

  1. Units

When carrying out calculations o...

July 20, 2017

Ketone and aldehydes are functional groups that organic compounds have. A ketone is C=O that is connected to a carbon on both sides. Therefore it is always found inside a chain and never at the end. Aldehyde, on the other hand is C=O that is connected to a carbon on one side and hydrogen on another. Therefore, aldehydes are found at the end of chains.

 To learn more organic chemistry and schedule a free consultation with...

July 17, 2017

The pH of a solution is 7. When acid is added to the solution, the hydronium ion concentration becomes 100 times greater. What is the pH of the new solution?

(1) 1  

(2) 5 

(3) 9

(4) 14 

Answer and Explanation:

First we need to understand the pH scale well. If pH less than 7, the solution is acid, equal to 7 is neutral and greater than 7 is basic. When acid is added to the solution, it should become more acidic and therefore...

July 15, 2017

Under which transformation would A B C , the image of ABC, not be congruent to ABC?

(1) reflection over the y-axis
(2) rotation of 90o clockwise about the origin
(3) translation of 3 units right and 2 units down
(4) dilation with a scale factor of 2 centered at the origin 

Explanation and answer:

The only transformation listed that changes the size of ABC is dilation, choice (4). Under dilation with a scale of 2, ABC will...

July 13, 2017

(1) +1

(2) +2

(3) +29

(4) +64 

Answer and explanation:

What particles are inside the nucleus of an atom? Protons and neutrons. Protons have a charge of plus one while neutrons have no charge (neutral). Therefore, the charge of nucleus of copper atom must be equal to the charge of the protons inside the nucleus. How many protons does Copper have? The number of protons is equal to atomic number which we can find by looking...

July 10, 2017

Which of the following aqueous solutions has the lowest freezing point?

(A) 0.2 m NaCl
(B) 0.2 m CaCl2

(C) 0.2 m H2SO4

(D) 0.2 m NH3
(E) 0.2 m Al(NO3)3 

Answer and Explanation:

Freezing point of a pure solvent depends on the amount of solute that gets dissolved in it. In order to determine which solution has the lowest freezing point, we need to look at the molality as well as whether the solute is ionic or covalent. Since...

July 8, 2017

Under which of the following conditions can an endothermic reaction be thermodynamically favorable?

(A) ΔG is positive (B) ΔS is negative (C) TΔS > ΔH (D) TΔS = 0

(E) There are no conditions under which an endothermic reaction can be thermodynamically favorable. 

Answer and explanation:

To be thermodynamically favorable, a reaction must have negative ΔG (Gibbs Free Energy). 

 The formula for Gibbs Free Energy is ΔG = ΔH...

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