Chemical equations are symbolic representations of chemical reactions that express the reactants and products in terms of their respective chemical formulae. They also use symbols to represent factors such as reaction direction and the physical states of the reacting entities.
Definition: A balanced chemical equation has the same number of atoms on the reactant and product sides for each element involved in the reaction. This is a condition that the equation must meet in order to be consistent with the law of conservation of mass and constant proportions. It can be confirmed by adding the numbers of atoms on either side of the arrow and comparing them to ensure they are equal. It is worth noting that the number of atoms for a given element is determined by multiplying the coefficient of any formula containing that element by the element’s subscript in the formula. If an element appears in more than one formula on a given side of the equation, the number of atoms represented in each formula must be computed and added together.
Balanced Chemical Equations Chemistry Questions with Solutions
Q1. A balanced chemical equation is in accordance with-
- Multiple proportion
- Reciprocal proportion
- Conservation of mass
- Definite proportions
Correct Answer: (c) Law of Conservation of Mass
Q2. The correct balanced equation for the reaction __C2H6O + __O2 → __CO2 + __H2O is-
- 2C2H6O + O2 → CO2 + H2O
- C2H6O + 3O2 → 2CO2 + 3H2O
- C2H6O + 2O2 → 3CO2 + 3H2O
- 2C2H6O + O2 → 2CO2 + H2O
Correct Answer: (b) C2H6O + 3O2 → 2CO2 + 3H2O
Q3. The correct balanced equation for the reaction __KNO3 + __H2CO3 → __K2CO3 + __HNO3 is-
- 2KNO3 + H2CO3 → K2CO3 + 2HNO3
- 2KNO3 + 2H2CO3 → K2CO3 + 2HNO3
- KNO3 + H2CO3 → K2CO3 + 2HNO3
- 2KNO3 + 2H2CO3 → K2CO3 + 3HNO3
Correct Answer: (a) 2KNO3 + H2CO3 → K2CO3 + 2HNO3
Q4. The correct balanced equation for the reaction __CaCl2 + __Na3PO4 → __ Ca3(PO4)2 + __ NaCl is-
- 2CaCl2 + 2Na3PO4 → 2Ca3(PO4)2 + NaCl
- CaCl2 + Na3PO4 → Ca3(PO4)2 + NaCl
- 3CaCl2 + 2Na3PO4 → Ca3(PO4)2 + 6NaCl
- 3CaCl2 + 2Na3PO4 → Ca3(PO4)2 + 3NaCl
Correct Answer- (c) 3CaCl2 + 2Na3PO4 → Ca3(PO4)2 + 6NaCl
Q5. The correct balanced equation for the reaction __TiCl4 + __H2O → __TiO2 + __HCl is-
- TiCl4 + 2H2O → TiO2 +2HCl
- TiCl4 + 2H2O → TiO2 + 4HCl
- 2TiCl4 + H2O → 2TiO2 + HCl
- TiCl4 + 4H2O → TiO2 + 4HCl
Correct Answer- (b) TiCl4 + 2H2O → TiO2 + 4HCl
Q6. Write a balanced equation for the reaction of molecular nitrogen (N2) and oxygen (O2) to form dinitrogen pentoxide.
Answer. The equation for the reaction is-
N2 + O2 → N2O5 (unbalanced equation)
The balanced chemical equation is-
2N2 + 5O2 → 2N2O5
Q7. On what basis is a chemical equation balanced?
Answer. A chemical equation is balanced using the law of conservation of mass, which states that “matter cannot be created nor destroyed.”
Q8. What is the balanced equation for the reaction of photosynthesis?
Answer. The balanced chemical equation for the reaction of photosynthesis is-
6CO2 + 6H2O → C6H12O6 + 6O2.
Q9. We must solve a skeletal chemical equation.” Give a reason to justify the statement.
Answer. Skeletal chemical equations are unbalanced. Due to the law of conservation of mass, we must balance the chemical equation. It states that ‘matter cannot be created or destroyed.’ As a result, each chemical reaction must have a balanced chemical equation.
Q10. What does it mean to say an equation is balanced? Why is it important for an equation to be balanced?
Answer. The chemical equation must be balanced in order to obey the law of conservation of mass. A chemical equation is said to be balanced when the number of different atoms of elements in the reactants side equals the number of atoms in the products side. Balancing chemical equations is a trial-and-error process.
Q11. What is meant by the skeletal type chemical equation? What does it represent? Using the equation for electrolytic decomposition of water, differentiate between a skeletal chemical equation and a balanced chemical equation.
Answer. Skeletal equations are those in which formulas are used to indicate the chemicals involved in a chemical reaction.
The law of conservation of mass does not apply to skeletal equations.
The chemical formulas are represented by balanced chemical equations, which follow the law of conservation of mass, which states that the atoms on the reactant and product sides are the same.
H2O → H2 + O2 : Skeletal equation
2H2O → 2H2 + O2 : Balanced chemical equation
Q12. Write the balanced chemical equation for the following reaction:
- Phosphorus burns in presence of chlorine to form phosphorus pentachloride.
- Burning of natural gas.
- The process of respiration.
- P4 + 10Cl2 → 4PCl5
- CH4 +2O2 → CO2 +2H2O + heat energy
- C6H12O6 + 6O2 + 6H2O → 6CO2 + 12H2O + energy
Q13. What Is the Distinction Between a Balanced Equation and a Skeleton Equation?
Answer. The primary distinction between a balanced equation and a skeleton equation is that the balanced equation provides the actual number of molecules of each reactant and product involved in the chemical reaction, whereas a skeleton equation only provides the reactants. Furthermore, a balanced equation may or may not contain stoichiometric coefficients, whereas a skeleton equation does not.
Q14. Balance the equations
- HNO +Ca(OH)2 → Ca(NO3)2 + H2O
- NaCl + AgNO3 → AgCl + NaNO3
- BaCl2 +H2SO4 → BaSO4 +HCl
Answer. The balanced chemical equation for the reactions are as follows-
- 2HNO3 + Ca(OH)2 → Ca(NO3)2 + 2H2O
- NaCl + AgNO3 → AgCl + NaNO3
- BaCl2 +H2SO4 → BaSO4 + 2HCl
Q15. Write a balanced molecular equation describing each of the following chemical reactions.
- Solid calcium carbonate is heated and decomposes to solid calcium oxide and carbon dioxide gas.
- Gaseous butane, C4H10, reacts with diatomic oxygen gas to yield gaseous carbon dioxide and water vapour.
- Aqueous solutions of magnesium chloride and sodium hydroxide react to produce solid magnesium hydroxide and aqueous sodium chloride.
- Water vapour reacts with sodium metal to produce solid sodium hydroxide and hydrogen gas.
- CaCO3 → CaO + CO2
On heating, 1 mol of solid calcium carbonate yields 1 mol of calcium oxide and 1 mol of carbon dioxide gas.
- 2C4H10 +13O2 → 8CO2 + 10H2O
When 2 moles of butane gas react with 13 moles of diatomic oxygen gas, 8 moles of carbon dioxide gas and 10 moles of water vapours are produced.
- MgCl2 + 2NaOH → 2NaCl + Mg(OH)2
1 mol magnesium Cordelia reacts with two moles of sodium hydroxide to produce two moles of aqueous sodium chloride solution and one mole of solid magnesium hydroxide.
- 2H2O + 2Na → 2NaOH + H2
2 moles of water vapour react with 2 moles of sodium metal, yielding 2 moles of solid sodium hydroxide and 1 mol of hydrogen gas.
Practise Questions on Balanced Chemical Equations
Balance the following equations-
1. (NH4)2Cr2O7(s) → Cr2O3 (s) + N2 (g) + H2O(g)
2. Ca(OH)2 + H3PO4 → Ca3(PO4)2 + H2O
3. FeCl3 + NH4OH → Fe(OH)3 + NH4Cl
4. Al2(CO3)3 + H3PO4 → AlPO4 + CO2 + H2O
5. S8 + F2 → SF6
Click the PDF to check the answers for Practice Questions.