Ob8 SC3 Learn the Basics

 

In a chemical reaction, atoms are never lost or gained. What is this called?

• The Atom Efficiency Rule

• The Law of Conservation of Mass

•  The Law of Mole Ratios

• The Rule of Reactivity

Why do we need to balance chemical equations?

• To make the equations easier to read.
• To ensure the conservation of mass and accurately represent chemical reactions.
• To increase the speed of chemical reactions.
• To reduce the number of reactants needed.

How many atoms of oxygen are in the following molecule?

(NH₄)₂O

• 1
• 2
• 0
• 3

How many atoms of nitrogen are in the following molecule?

(NH₄)₂O

• 3
• 4
• 1
• 2

How many atoms of hydrogen are in the following molecule?

(NH₄)₂O

• 6
• 4
• 8
• 10

• 1
• 3
• 4
• 2

• 2 hydrogen atoms on each side.
• 6 hydrogen atoms on each side.
• 4 hydrogen atoms on the left, 2 on the right.
• 4 hydrogen atoms on each side.

Answer explanation

Which of the following chemical equations are correctly balanced?

• H₂ + Cl₂ -> 2HCl

• 2H₂ + O₂ -> H₂O

• Na + O₂ -> Na₂O

• 2Na + Cl₂ -> 2NaCl.

Which of the following tips about balancing equations are correct?

• Always check your atom counts at the end

• You can change the subscripts

• Watch out for elements that appear in more than one compound

• Coefficients should only be whole numbers