Chemical Equations/Law of Conservation of Mass

In the equation 2Mg + O₂ ---> 2MgO, what is the coefficient of the oxygen molecule?

• 0

• 1

• 2

• 4

Tags

NGSS.MS-PS1-5

In the equation 2Mg+O₂--->2MgO, what is the subscript of the oxygen molecule?

• 0

• 1

• 2

• 3

Tags

NGSS.MS-PS1-1

New substances formed during a chemical reaction are indicated ________________________.

• on the left side of the equation and are called products.

• on the right side of the equation and are called reactants.

• on the left side of the equation and are called reactants

• on the right side of the equation and are called products.

Which of the following is a TRUE statement?

• In a chemical equation, you can change the number of atoms in each molecule.

• In a chemical equation, you can end up with different numbers of atoms of an element on the reactant side for the same element on the product side.

• In a chemical equation, an element or compound must be accompanied by a phase change.

• In a chemical equation, the coefficients tell you the number of molecules of each reactant used, and the number of molecules of each product made.

Tags

NGSS.MS-PS1-5

What does the arrow in the equation mean?

• equals

• turns into

• yields

• creates

All chemical equations must be balanced. This means that the same number of atoms of each of the elements must be found in both the reactants and the products of the reaction. Which scientific law does this illustrate?

• Law of Superpostition

• Law of Conservation of Energy

• Law of Conservation of Mass

• Law of Reflection

Tags

NGSS.MS-PS1-5

Which reaction between methane gas and oxygen best supports the law of conservation of mass?

• CH_{4 +} O_{2 --->} CO₂ + H₂O

• CH_{4 +} 2O_{2 --->} CO₂ + 2H₂O

• 2CH_{4 +} O_{2 --->} 2CO₂ + 2H₂O

• 2CH_{4 +} 2O_{2 --->} 2CO₂ + 3H₂O

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2

A student placed 2g of baking soda in a balloon and 100mL of vinegar in an Erlenmeyer flask. After stretching the opening of the balloon across the neck of the flask, the student raised it to dump the baking soda into the flask. He immediately observed foaming bubbles in the flask and the balloon began to expand. The student concluded that_____.

• a physical change only was occurring.

• the bubbles indicated a chemical change was occurring.

• the baking soda and vinegar were products of a chemical reaction.

• the gas was oxygen.

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2

What are coefficients?

• the number written to the left and below the element.

• the number written to the right and below the element.

• the number written anywhere in a chemical equation.

• the number written in front of the molecules in a chemical equation.

Which reaction between hydrogen gas and oxygen gas best supports the law of conservation of mass?

• H₂ + O₂ ---> H_2O

• H + O ---> H₂O

• H₂ + 2O --->2H₂O

• 2H₂ + O₂ ---> 2H₂O

Tags

NGSS.MS-PS1-5