Chemical Equations

Which of the following chemical equations is balanced?

• H2 + O2 → H2O

• Na + Cl2 → NaCl

• CO2 + H2O → CH4 + O2

• N2 + 3H2 → 2NH3

How many hydrogen (H) atoms are there in the product side of the equation CH4 + 2O2 → CO2 + 2H2O?

• 2

• 4

• 6

• 8

Answer explanation

Looking at the product side of the given equation, we see CO2 and 2H2O. While CO2 contains no hydrogen atoms, each H2O molecule contains two hydrogen atoms. Since there are two H2O molecules, we multiply 2*2 to find that there are a total of four hydrogen atoms on the product side of the equation.

Which of the following elements is not present in the balanced chemical equation 2H2 + O2 → 2H2O?

• Hydrogen (H)

• Oxygen (O)

• Carbon (C)

• None of the above

Answer explanation

The question asks which element is not present in the given chemical equation. The equation includes Hydrogen (H) and Oxygen (O) as they are part of the reactants and the product. However, Carbon (C) is not present anywhere in the equation, making it the correct answer.

In the chemical equation 4Fe + 3O2 → 2Fe2O3, how many iron (Fe) atoms are on the reactant side?

• 2

• 3

• 4

• 8

Answer explanation

The question is asking about the number of iron (Fe) atoms on the reactant side of the given chemical equation. From the equation 4Fe + 3O2 → 2Fe2O3, we can see that there are '4' iron (Fe) atoms on the reactant side. Therefore, the correct choice is '4'.

Which of the following equations is unbalanced?

• C6H12O6 → 2C2H5OH + 2CO2

• N2 + 3H2 → 2NH3

• 2KClO3 → 2KCl + 3O2

• 4P + 5O2 → P4O10

Answer explanation

The given question asks us to identify the unbalanced equation. The correct answer is 'C6H12O6 → 2C2H5OH + 2CO2'. Looking at this equation, we can see that the number of carbon, hydrogen and oxygen atoms are not the same on both sides, hence it's unbalanced.

How many carbon (C) atoms are there in the product side of the equation C3H8 + 5O2 → 3CO2 + 4H2O?

• 3

• 6

• 9

• 12

Answer explanation

The question asks about the number of carbon atoms on the product side of the chemical equation C3H8 + 5O2 → 3CO2 + 4H2O. The product side of the equation has 3 molecules of CO2 (carbon dioxide). Each molecule of CO2 has one carbon atom. Therefore, there are 3 carbon atoms on the product side of the equation. So, the correct answer is '3'.

Which of the following equations follows the law of conservation of mass?

• H2 + O2 → H2O

• NH4NO3 → N2O + 2H2O

• CH4 + O2 → CO2 + H2O

• 2H2 + Cl2 → 2HCl

Answer explanation

The law of conservation of mass states that matter cannot be created or destroyed in an isolated system. The equation 'CH4 + O2 → CO2 + H2O' follows this law. On the left side, there are 1 carbon, 4 hydrogen, and 2 oxygen atoms. On the right side, there are also 1 carbon, 4 hydrogen, and 2 oxygen atoms, meaning mass has been conserved.

How many oxygen (O) atoms are there combined on both the reactant and product sides of the equation 2KClO3 → 2KCl + 3O2?

• 3

• 6

• 9

• 12

Answer explanation

The equation shows that 2 molecules of KClO3 are decomposed. Each KClO3 molecule contains 3 oxygen (O) atoms. Hence, on the reactant side, there are 2*3 = 6 O atoms. On the product side, there are 3 molecules of O2, each containing 2 O atoms, 3*2 = 6 O atoms. Therefore, combined on both sides, we have 6 + 6 = 12 O atoms. The correct answer is 12.

In the balanced chemical equation C4H10 + 6.5O2 → 4CO2 + 5H2O, what is the coefficient that needs to be adjusted to make it a whole number?

• 4

• 6.5

• 5

• 10

In the chemical equation 2Na + 2H2O → 2NaOH + H2, how many sodium (Na) atoms are there on the product side?

• 1

• 2

• 3

• 4