Atoms in Chemical Reactions

The Law of Conservation of Mass states that matter cannot be created nor __________________.

• destroyed

• rearranged

• transferred

• changed

Tags

NGSS.MS-PS1-5

The following chemical reaction occurs:

2S + 3O₂ --> 2SO₃

_{How many atoms of oxygen are present in the reactants?}

• 2 atoms of oxygen

• 3 atoms of oxygen

• 6 atoms of oxygen

• 1 atom of oxygen

There are two reactants in a chemical equation, and one product. The mass of the product is 30g. The mass of the first reactant is 17g. What must the mass of the second reactant be, if the equation is to follow the Law of Conservation of Mass?

• 3g

• 13g

• 30g

• Impossible to determine with the information given

A student reacts baking soda & vinegar inside a CLOSED plastic bag.

Which of the following would provide evidence that the number of atoms present before the chemical reaction is equal to the number of atoms present after the chemical reaction?

• The mass of the closed plastic bag, baking soda, and vinegar before the reaction is equal to the mass after the reaction.

• Bubbles are produced during the reaction, which means that a gas was being produced.

• The plastic bag did not change in any way, indicating that it is not involved in the reaction.

• The mass of the baking soda added is exactly equal to the mass of the vinegar added.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

2Ca + O₂ --> ___ CaO

What coefficient should be added in front of CaO to finish balancing this chemical equation?

• 1

• 2

• 3

• 4

How many iron (Fe) atoms are present in this chemical formula?

• 4 iron atoms

• 2 iron atoms

• 8 iron atoms

• 3 iron atoms

A chemical reaction is balanced when __________.

• both sides have the same elements

• both sides have the same number of atoms of each element

• both sides have the same subscripts

• both sides have the same coefficients

Tags

NGSS.MS-PS1-5

The number in front of a compound or element is called a _________.

• Subscript

• Coefficient

• Superscript

• Charge

The small number on the lower right of an element in a chemical formula is called a __________.

• Subscript

• Superscript

• Coefficient

• Charge

Mg + ___ HCl → MgCl₂ + H₂

_{Fill in the missing coefficient in order to balance this chemical reaction.}

• 1

• 2

• 3

• 4