8.P.1.4 - Balance Equations

Which best describes how to balance the chemical equation Mg + O₂ → MgO to support the law of conservation of mass?

• Add the coefficient 2 before the Mg on both sides of the equation.
• Add the coefficient 2 before the O2 on the left side of the equation.
• Add the coefficient 2 before the Mg on the left side of the equation.
• Add the coefficient 2 before the MgO on the right side of the equation.

Tags

NGSS.MS-PS1-5

Zn + 2HCl → ZnCl₂ + H₂ In this equation, suppose 11 grams of zinc react with 12 grams of hydrogen chloride to form 16 grams of zinc chloride and an unknown amount of hydrogen gas. Based on the Law of Conservation of Mass, how many grams of hydrogen gas will form?

• 7 grams
• 1 gram
• 19 grams
• 39 grams

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

The equation shows a reaction between sodium (Na) and water (H₂O).

2Na (s) + H₂O (l) → 2NaOH (aq) + H₂ (g)

Which best explains why the equation is not balanced?

• There is not enough water in the reactants.
• There is too much sodium in the reactants.
• There is too much hydrogen gas in the products.
• There is not enough sodium hydroxide in the products.

Tags

NGSS.MS-PS1-5

The reaction CaCO₃ → CaO + CO₂ takes place in a closed system. Which best describes this balanced equation?

• Reactants and products are equal in the chemical reaction.
• More products and less reactants are produced.
• More reactants and less products are produced.
• The equation is not balanced.

Tags

NGSS.MS-PS1-5

Which products would balance the equation

CaCl₂ + 2Li → ?

• none of these

• 2LiCl + Ca
• LiCl + Ca
• Li2Cl + Ca

Tags

NGSS.MS-PS1-5

A chemical reaction is represented by the equation

BeO + 2NaCl → Na₂O + _______.

Which substance would make the equation true and balanced?

• BeCl₂

• BeO
• Be₂Cl

• 3Be₂Cl

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

A chemical reaction is 2H₂O → 2H₂ + O₂. Based on the law of conservation of mass, how much hydrogen gas is produced compared to the amount of oxygen produced?

• twice as much
• half as much
• the same amount
• four times as much

Tags

NGSS.MS-PS1-5

What is the total number of oxygen atoms on the reactant side of the equation CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂?

• 5
• 2
• 3
• 7

Tags

NGSS.MS-PS1-1

The chemical reaction 2H₂O₂ → 2H₂O + O₂ occurs. How many atoms of hydrogen are involved in the reaction?

• 4
• 1
• 2
• 8

Tags

NGSS.MS-PS1-5

Sam followed the lab procedures shown in the image to complete an experiment. Which best describes Sam’s conclusion?

• No change in mass occurred after heating.
• A change in mass occurred after heating.
• A physical change occurred, producing new products.
• A chemical change occurred, producing new reactants.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5