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Balancing Chemical Equations

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Balancing Chemical Equations

A reaction rearranges atoms; it does not create or destroy them. Balance each equation by changing coefficients (numbers in front of formulas), never the subscripts inside formulas. Use the smallest whole-number coefficients. A blank coefficient means 1.

Read the reaction

A science team is checking equations for a reaction-safety database. Help them make sure the atom count is conserved.

1.For the equation 2H₂ + O₂ → 2H₂O, name the reactants and the product.

2.Which statement best describes conservation of mass in a chemical reaction?

Atoms are made during the reaction, so products have more mass.
The total mass stays the same because atoms are rearranged, not created or destroyed.
Some atoms disappear when products form.
Only the number of molecules must stay the same.

Atom

Left side

Right side

3.Using the atom-count ledger for Mg + O₂ → MgO, is the equation balanced? State which element is unbalanced and how many atoms of it are on each side.

4.Why must you change a coefficient rather than changing the subscript in a formula when balancing an equation?

Balance the reaction set

Work methodically: count atoms, adjust coefficients, then recount every element on both sides.

5.Balance the equation using the smallest whole-number coefficients: Mg + O₂ → MgO. Write the completed equation.

6.Balance the equation for iron reacting with oxygen: ___Fe + ___O₂ → ___Fe₂O₃. Give the smallest whole-number coefficients.

7.Methane burns in oxygen to form carbon dioxide and water. Balance: CH₄ + O₂ → CO₂ + H₂O. Include the coefficients in order.

8.Balance this reaction: ___Al + ___CuSO₄ → ___Al₂(SO₄)₃ + ___Cu. Treat the sulfate group as a unit while counting, then give the smallest whole-number coefficients.

9.A student says the balanced equation for hydrogen reacting with oxygen is H₂ + O₂ → H₂O₂. Explain why this is not a valid way to balance the equation, then give the correctly balanced equation for forming water, H₂O.

10.Describe a reliable sequence of steps for balancing an equation. Include how you check that your final coefficients are in the simplest ratio.