November 17, 2019

What is the chemical name of the compound NH4SCN?

(1) ammonium thiocyanate

(2) ammonium cyanide
(3) nitrogen hydrogen cyanide

(4) nitrogen hydrogen sulfate

Answer: (1) ammonium thiocyanate

Explanation: In order to name a compound, we must first figure out whether it is ionic or covalent. Ionic compounds can be divided into three categories: metal + nonmetal, meta+ polyatomic ion, polyatomic ion+ polyatomic ion, polyatomic io...

November 13, 2019

 Which electron configuration represents the electrons in an atom of sulfur in an excited state?

(1) 2 – 8 – 6

(2) 2 – 7 – 7

(3) 2–8– 7

 (4) 2–7– 8

Answer : 2) 2-7-7

Explanation: We must first look at the Periodic Table at the Reference Table, and find Sulfur. Sulfur's electron configuration is 2-8-6 according to the Reference Table. An excited state is a state in which an electron jumps to a higher energy level, while the g...

November 11, 2019

What is the color of bromcresol green indicator in a solution with a pH value of 2.0?

(1) blue

(2) green

(3) red

(4) yellow

Answer: Choice 4

Solution: An indicator allows us to figure out the pH range of the solution and whether it is acidic or basic. To do this problem, we need to look at Table M of the Regent Reference Table, Common Acid–Base Indicators. 

According to the table, bromcresol green, has a pH range for co...

October 27, 2019

The BA-Md program at Brooklyn college is an eight year program that includes four undergraduate years at Brooklyn college and four more years at SUNY Downstate medical school. 

This program is amazing for saving future doctors a ton of money, since CUNY Brooklyn is a city college with a city tuition and SUNY Downstate is a state medical school with reduced tuition as well. The program also has a guaranteed admission to a...

October 23, 2019

To convert grams to moles and vice versa, we must always use Molar Mass.

Molar Mass can be calculated using the Periodic Table.

To calculate the molar mass, we multiply each atom in the molecule by its atomic mass found in the Periodic Table and multiply by the number of atoms.

For example, to calculate the molar mass of CO2

C= 1*12.011 = 12.011

O= 2*15.999 = 31.998

12.011 + 31.998 = 44.009 g/mol

To convert grams to moles, we...

October 21, 2019

Lactic acid has one acidic hydrogen. A 0.1 M solution of lactic acid has a pH of 2.44. Calculate Ka for lactic acid? When we do acid/base questions, we always need to ask ourselves 2 questions.

Question1 Do we have an acid or a base?

In this case the question itself, told us that we are dealing with an acid.

Question 2 Is this a weak or a strong acid?

Strong acids are: HCl - hydrochloric acid HNO3 - nitric acid H2SO4 - sulf...

October 16, 2019

Will precipitation occur when the following solutions are mixed? If so, write a balanced chemical equation for the reaction.

(a) Na2CO3 and AgNO3, (b) NaNO3 and NiSO4, (c) FeSO4 and Pb(NO3) 2

In order for precipitation occur, we must first write out the products of each reaction. These are double replacement reactions, where we can use the following formula: AB+CD --> AD + CB to predict the products. We also need to remem...

October 9, 2019

Draw the structural formula for at least one bromoalkene with the molecular formula C5H9Br that shows:

(a) Neither E,Z isomerism nor chirality.

(b) E,Z isomerism but not chirality.

(c) Chirality but not E,Z isomerism.

(d) Both chirality and E,Z isomerism.

In order to do this questions we must know two things. A molecule that does not have a chiral center will not be chiral. A chiral center is a carbon that is attached to fou...

October 8, 2019

Which notations represent atoms that have the same number of protons but a different number of neutrons?

                                               

(1) H-3 and He-3

(2) S-32 and S-32

(3) Cl-3...

October 2, 2019

Which compounds contain chiral centers?

(a) 2-Chloropentane

(b) 3-Chloropentane

(c) 3-Chloro-1-pentene

(d) 1,2-Dichloropropane

A chiral center is a carbon that is attached to 4 different groups.

We should start by drawing out molecules, and adding the necessary number of hydrogens to each carbon. Remember a carbon wants to always have 4 bonds. Therefore, if we see a carbon with 2 bonds, we attach 2 more hydrogens and so f...

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