5th - Counting Atoms, Classifying and Balancing Equations

Front

What is a coefficient in a chemical equation?

Back

A coefficient is a number placed in front of a chemical formula in an equation to indicate how many molecules or moles of that substance are involved in the reaction.

Front

How do you determine if a chemical equation is balanced?

Back

A chemical equation is balanced when the number of atoms of each element is the same on both sides of the equation.

Front

What is the balanced equation for the reaction of nitrogen and oxygen to form nitric oxide?

Back

The balanced equation is N₂ + 2O₂ → 2NO.

Front

What does it mean for a chemical equation to be unbalanced?

Back

An unbalanced equation has unequal numbers of atoms of one or more elements on either side of the equation.

Front

How many HCl molecules are needed to balance the equation Mg + __HCl → MgCl₂ + H₂?

Back

2 HCl molecules are needed to balance the equation.

Front

What is the significance of balancing chemical equations?

Back

Balancing chemical equations is important because it follows the law of conservation of mass, ensuring that matter is neither created nor destroyed in a chemical reaction.

Front

Identify the unbalanced equation: CaCO₃ → CaO + CO₂, PbO₂ + 2H₂ → 2Pb + H₂O, 2Na + 2H₂O → 2NaOH + H₂, CS₂ + 3O₂ → CO₂ + 2SO₂.

Back

The unbalanced equation is PbO₂ + 2H₂ → 2Pb + H₂O.

Front

What are the coefficients for the reaction PCl₅ + __H₂O → __HCl + H₃PO₄?

Back

The coefficients are 4 for H₂O and 5 for HCl.

Front

What is the law of conservation of mass?

Back

The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction; the total mass of reactants equals the total mass of products.

Front

What is a reactant in a chemical reaction?

Back

A reactant is a substance that undergoes change during a chemical reaction.