Chemical Reaction and Conservation of Mass

Formation of a precipitate is an evidence of a chemical reaction. True or False

• True

• False

• Can't Tell

Tags

NGSS.MS-PS1-2

In a chemical reaction, 300 grams of reactant A

are combined with 100 grams of reactant B. Both A and B react to

completion. How much will the product weigh?

• 100 g

• 200 g

• 300 g

• 400 g

Tags

NGSS.MS-PS1-5

In a reaction, 25 grams of reactant AB breaks

down into 10 grams of product A and an unknown amount of product B.

Using the law of conservation of mass, how much does product B weigh?

• 10 g

• 15 g

• 20 g

• 25 g

Tags

NGSS.MS-PS1-5

Which of the following statements best defines the law of conservation of mass?

• Mass cannot be created but it can be destroyed under extreme pressures.

• Mass cannot be conserved during a chemical reaction; a little bit of mass is always lost.

• The mass of a closed system cannot change over time; mass cannot be created nor destroyed.

• When added to a system, energy can destroy mass.

Tags

NGSS.MS-PS1-5

Burning of Magnesium is a chemical reaction because

• a precipitate is formed

• there is a colour change

• a gas is given off

• there is a change of state

Tags

NGSS.MS-PS1-2

Evidence that a reaction has occurred includes

• change of color

• formation of a precipitate

• release of gas bubbles

• all of these

Tags

NGSS.MS-PS1-2

What are the reactants in this chemical equation?

6O₂ + C₆H₁₂O₆ -> 6CO₂ + 6H₂O + ENERGY

• CO₂ + H₂O

• ENERGY

• O₂ + C₆H₁₂O₆

• C₆H₁₂O₆ + H₂O

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

How many atoms of aluminum are on each side of the following equation: 4Al + 3O₂ --> 2Al₂ O₃

• 1

• 2

• 3

• 4

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-5

teacher is demonstrating physical and chemical changes to her class. Which action should she use to demonstrate a chemical change?

• burning a piece of paper

• tearing a piece of paper

• cutting a piece of paper

• folding a piece of paper

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

A science teacher lit a candle and described to his students that some of the wax is burning while some of the wax is melting. Student A states that these are both physical changes. Students B states that these are both chemical changes. Which statement BEST describes the students' conclusions?

• Student A is correct.

• Student B is correct.

• Both are incorrect, because burning wax is a chemical change and melting wax is a physical change.

• Both are incorrect, because burning wax is a physical change and melting wax is a chemical change.

Tags

NGSS.MS-PS1-2