Which set of numbers correctly balances the following chemical equations?

____Na + ___O₂ → ___Na₂O

A. 1, 3, 1
Incorrect. Neither element is balanced with these coefficients.

B. 2, O, 2
Incorrect. There are two sodium atoms on the left and four sodium atoms on the right.

C. 4, O, 2
Correct! There are four sodium atoms and two oxygen atoms on each side.

D. 4, O, 4
Incorrect. There are four sodium atoms on the left and eight sodium atoms on the right.

The correct value for the coefficient of water when the following equation is balanced is —

___ NaOH + ___ H₂SO₄ → ___ Na₂SO₄ + ___ H₂O

A. 1
Incorrect. You need more than one water to balance the equation.

B. 2
Correct! The balanced equation has coefficients of 2:1:1:2.

C. 3
Incorrect. Be careful since two reactants have hydrogen in them.

D. 4
Incorrect. You must use the lowest whole number possible.

When the equation is balanced, in which of the following chemical reactions is the value for the coefficient of hydrogen gas the greatest?

A. H₂ + Cl₂ → HCl
Incorrect. The coefficient for hydrogen in the balanced equation is one, which is the least. Find the greatest.

B. H₂ + C → CH₄
Incorrect. The coefficient for hydrogen in the balanced equation is two, but it is not the greatest in the set.

C. H₂ + N₂ → NH₃
Correct! The coefficient for hydrogen in the balanced equation is three.

D. H₂ + O₂ → H₂O
Incorrect. The coefficient for hydrogen in the balanced equation is two, but it is not the greatest in the set.

Which of the following reactions supports the law of conservation of mass?

A. 2C₂H₆ + 3O₂ → 4CO₂ + 3H₂O
Incorrect. The equation is not balanced.

B. 2C₂H₆ + 7O₂ → 4CO₂ + 5H₂O
Incorrect. The equation is not balanced.

C. C₂H₆ + 3O₂ → 4CO₂ + 6H₂O
Incorrect. The equation is not balanced.

D. 2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O
Correct! The equation is balanced.