Chemistry EOG Review

Which of the following is a compound?

• sodium

• sugar

• nitrogen

• air

Answer explanation

Sodium and Nitrogen are both on the periodic table so they are elements. Air is a homogenous mixture of oxygen, nitrogen, carbon dioxide and water vapor. Sugar is a compound of carbon, hydrogen and oxygen sharing valence electrons.

Tags

NGSS.MS-PS1-1

• several molecules of water are produced

• the mass of the carbon atoms is reduced during this reaction

• the mass of the atoms in the reactant equals the mass of the atoms in the products

• the mass of the hydrogen atoms is the only thing that remains the same before and after the reaction

Answer explanation

The Law of Conservation of Mass states that the mass of the reactants will equal the mass of the products in a closed system.

Tags

NGSS.MS-PS1-5

Which is classified as an element?

• carbon dioxide

• iron

• vinegar

• water

Answer explanation

Iron is the only answer choice that is on the periodic table (Fe). The rest are compounds.

Which best describes the sequences of the elements in Period 5 of the periodic table?

• highly reactive gases, relative nonreactive metals, metalloids, very nonreactive gases, nonreactive nonmetals

• highly reactive metals, relatively nonreactive metals, metalloids, reactive nonmetals, nonreactive gases

• nonreactive gases, metalloids, nonreactive metals, highly reactive metals, highly reactive gases

• nonreactive gases, nonreactive metals, highly reactive metals, metalloids, reactive nonmetals, reactive gases

Answer explanation

A period is a row on the periodic table. All rows start with highly reactive metals followed by less reactive metals and ends with highly reactive nonmetals and finally nonreactive gases.

Which statement is true about a chemical reaction?

• the physical states of the atoms in the reaction determine the products

• some of the atoms in the reactants will be part of the products

• the number of atoms in the reactants determines the products

• all of the atoms in the reactants will be a part of the products

Answer explanation

According the the Law of Conservation of Mass - ALL of the atoms of the reactants will be part of the products. (Elements stay the same, just get rearranged).

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Chlorine has 7 valence electrons. With what group of elements will chlorine most readily bond?

• group 1

• group 2

• group 16

• group 18

Answer explanation

Eight is great! Chlorine has 7 valence electrons. It just needs 1 more to be stable. The alkali metals in Group 1 all have 1 valence electron.

Which is the best example of a chemical change?

• butter melting

• egg cooking

• paper tearing

• water evaporating

Answer explanation

All changes in state (evaporation, melting, freezing) are physical changes. Changes in odor such as when cooking an egg indicate chemical change.

Tags

NGSS.MS-PS1-2

Which chemical equation best represents the Law of Conservation of Mass?

Answer explanation

When ever it ask about the Law of Conservation of Mass, it wants to know which equation is balanced. Remember coefficients get multiplied through the whole compound.

Tags

NGSS.MS-PS1-5

Which is the best example of a pure substance?

• peanuts

• milk

• gold

• air

Answer explanation

Elements and compounds are pure substances. Mixtures are made up of 2 or more substances physically combined.

Which best explains how periods on the periodic table are organized?

• increasing atomic number from left to right

• increasing number of neutrons from left to right

• decreasing number of electrons from left to right

• decreasing atomic mass from left to right

Answer explanation

The perodic table is arranged according to the atomic number or number of protons.