Regents Chemistry 5

Question 1

Which of the following describes a chemical property of iron?

Accepted Answer

Iron reacts with oxygen to form rust

Answer

The ability to rust (react with O₂ and H₂O to form Fe₂O₃·nH₂O) is a chemical property because it involves a change in chemical composition.

Question 2

According to Le Chatelier's Principle, increasing pressure on a gaseous equilibrium shifts the reaction toward:

Accepted Answer

The side with fewer moles of gas

Answer

Increasing pressure shifts equilibrium toward the side that reduces pressure, which is the side with fewer moles of gas.

Question 3

What type of isomers have the same molecular formula and connectivity but differ in the spatial arrangement of atoms?

Accepted Answer

Stereoisomers

Answer

Stereoisomers (including enantiomers and diastereomers) share the same molecular formula and bond connectivity but differ in three-dimensional arrangement.

Question 4

Which of the following solutions is the most concentrated?

Accepted Answer

2.0 M NaCl

Answer

Molarity (M) measures moles of solute per liter of solution; 2.0 M has the most moles of NaCl per liter and is therefore most concentrated.

Question 5

What is the half-life of a radioactive isotope if 75% of a sample decays in 20 years?

Accepted Answer

10 years

Answer

After one half-life, 50% remains; after two half-lives, 25% remains (75% decayed). Two half-lives = 20 years, so one half-life = 10 years.

Regents Practice Test

Regents Practice Test

Regents Chemistry 5