October 27, 2017

When a chemical reaction is at equilibrium,
the concentration of each reactant and the  concentration of each product must be

(1) constant

(2) variable

(3) equal

 (4) zero

Answer and Explanation:

Most chemical reactions do not go to completion, but rather reach equilibrium. This is a state in which the rate of the forward reaction is equal to the rate of the reverse reaction. As reactants are making products, products are m...

October 18, 2017

What is the number of electrons shared in the multiple carbon-carbon bond in one molecule of 1-pentyne?

(1) 6

(2) 2

(3) 3

(4) 8 

Answer and Explanation: 

Pentyne is an organic compound. We know from looking at the ending "yne" that this molecules belongs to the class of alkynes if we look at the Reference table. Alkynes are molecules that have a triple bond. Since the question asks us for the number of electrons shared in m...

October 15, 2017

A sample of water is boiling as heat is added at a constant rate. Which statement describes the potential energy and the average kinetic energy of the water molecules in this sample?

(1) The potential energy decreases and the average kinetic energy remains the same.

(2) The potential energy decreases and the average kinetic energy increases.

(3) The potential energy increases and the average kinetic energy remains the same...

October 12, 2017

Which type of reaction involves the transfer of electrons?

(1) alpha decay
(2) double replacement

(3) neutralization
(4) oxidation-reduction 

Answer and Explanation:

Alpha decay is a type of nuclear reaction where the nucleus of parent atom breaks down and releases alpha particle( Helium atom) as well as a new atom. 

In a double replacement reaction, two ionic compounds come together  and switch their partners. Thus, t...

October 6, 2017

Which formula represents an alkane?

(1) C2H2

(2) C2H4

(3) C3H4

(4) C3H8 

Answer and Explanation: The general formula for an alkane is CnH2n+2. Therefore all we need to do is plus the carbon subscript and find out how many hydrogens are needed to make the formula an alkane. Let's start with choice 1: C2H2, If we plug in 2 for n, we see H must be 2*2+2=6. 

2: C2H4, the number of Hydrogens is still not 6 and is therefore not...

September 15, 2017

What is the chemical formula of sodium sulfate?

(1) Na2SO4     (2) Na2SO3

(3) NaSO4       (4) NaSO3 

Answer and Explanation: Too write a chemical formula from a name, we must first determine whether the compound is ionic or covalent. Since sodium is a metal (on the left on periodic table), sodium sulfate must be an ionic compound. Next, we will write the symbols for the two ions with their corresponding...

September 12, 2017

Which compound is an isomer of C2H5OC2H5?


(2) C2H5COOCH3

(3) C3H7COCH3

(4) C4H9OH 

Answer and Explanation:

Isomers are compounds that have exactly the same number of atoms of same elements but different structure. Therefore, we first need to count numbers of atoms in the compound C2H5OC2H5. There are 4 Carbon atoms, 10 Hydrogen atoms and 1 oxygen atom. Let's compare this to the number of atoms in the answer cho...

September 9, 2017

What occurs when a catalyst is added to a chemical reaction?

  1.   an alternate reaction pathway with a lower activation energy

  2.  an alternate reaction pathway with a higher activation energy

  3.   the same reaction pathway with a lower activation energy

  4.   the same reaction pathway with a higher activation energy 

Answer and Explanation: Catalysts are used to speed up reactions. How do they do so? Cataly...

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...

February 18, 2017

Which formula represents an alkane? (1) C2H2 (3) C3H4 (2) C2H4 (4) C3H8  Alkanes are a category of organic compounds. The generic formula for alkanes is CnH2n+2. What does it mean?

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