8.1 ✨Reactions and Equations

A balanced chemical equation is a direct presentation of the __________.

• law of conservation of mass

• law of definite proportions

• law of multiple proportions

• law of constant composition

Tags

NGSS.HS-PS1-7

In a chemical equation, the number written in front of the chemical formula is the __.

• coefficient

• subscript

• exponent

• molar mass

Balance the following equation. What is the coefficient for hydrogen fluoride? SiO₂ + HF ➔ SiF₄ + H₂O.

• 4

• 2

• 3

• 5

Tags

NGSS.HS-PS1-7

Which of the following is the correct word equation for the reaction: Cu(s) + O₂(g) ➔ CuO(s)?

• Copper(s) + Oxygen(g) ➔ Copper(II) Oxide(s)

• Copper(s) + Oxygen(g) ➔ Copper Oxide(s)

• Copper(s) + Oxygen(g) ➔ Copper(I) Oxide(s)

• Copper(s) + Oxygen(g) ➔ Copper Dioxide(s)

Why is it important to reduce coefficients in a balanced equation to the lowest-possible whole-number ratio?

• To make the equation easier to read

• To clearly indicate the relative amounts of substances in a reaction

• To ensure the equation is balanced

• To simplify calculations

Tags

NGSS.HS-PS1-7

What is the balanced chemical equation for the reaction between aqueous phosphoric acid and aqueous calcium hydroxide to form solid calcium phosphate and water?

• 2H₃PO₄(aq) + 3Ca(OH)₂(aq) ➔ Ca₃(PO₄)₂(s) + 6H₂O(aq)

• H₃PO₄(aq) + Ca(OH)₂(aq) ➔ Ca₃(PO₄)₂(s) + H₂O(aq)

• 3H₃PO₄(aq) + 2Ca(OH)₂(aq) ➔ 2Ca₃(PO₄)₂(s) + 3H₂O(aq)

• 2H₃PO₄(aq) + Ca(OH)₂(aq) ➔ Ca₃(PO₄)₂(s) + 2H₂O(aq)

Tags

NGSS.HS-PS1-7