Question

Balance the following by filling in missing species and proper coefficient: (a) \(\mathrm{NaOH}+\ldots \mathrm{NaHSO}_{4}+\mathrm{HOH}\) (b) \(\mathrm{PCT} 3+\mathrm{HOH} \rightarrow \ldots+3 \mathrm{HCl}\) (c) \(\mathrm{CH}_{4}+\underline{\mathrm{CCl}_{4}+4 \mathrm{HCl}}\)

Short answer

The balanced chemical equations are as follows: (a) \(NaOH + H_2SO_4 \rightarrow NaHSO_4 + H_2O\) (b) \(PCl_3 + H_2O \rightarrow H_3PO_3 + 3 HCl\) (c) \(CH_4 + 4 Cl_2 \rightarrow CCl_4 + 4 HCl\)

Step-by-step solution

Identify the missing species

In this reaction, we can see that NaOH reacts with an unknown compound, resulting in the formation of sodium hydrogen sulfate (NaHSO4) and water (H2O). We need to determine the missing reactant.

Identify the missing species by using the conservation of mass

According to the conservation of mass, the total mass of the reactants must be equal to the total mass of the products. From the equation, we can see that the missing species must have sulfur and oxygen atoms. Since NaOH is a strong base, it will react with an acid to form salt and water. The most suitable candidate for the missing reactant here is sulfuric acid (H2SO4).

Balance the equation

We now have the complete equation: \(NaOH + H_2SO_4 \rightarrow NaHSO_4 + H_2O\). This chemical equation is already balanced in terms of the number of atoms for each element on both the reactant and product sides. (b) \(PCl_3 + H_2O \rightarrow ... + 3 HCl\)

Identify the missing species

In this reaction, we know that phosphorus trichloride (PCl3) reacts with water (H2O) to form an unknown compound and hydrochloric acid (HCl). We need to determine the missing product of this reaction.

Identify the missing species by using the conservation of mass

According to the conservation of mass principle, the unknown product must contain phosphorus and oxygen atoms. Since PCl3 is an inorganic chloride, it will react with water to form an inorganic oxyacid. The most suitable candidate for the missing product here is phosphorous acid (H3PO3).

Balance the equation

Now we have the complete equation: \(PCl_3 + H_2O \rightarrow H_3PO_3 + 3 HCl\). This chemical equation is already balanced in terms of the number of atoms for each element on the reactant and product sides. (c) \(CH_4 + ... \rightarrow CCl_4 + 4 HCl\)

Identify the missing species

In this reaction, methane (CH4) reacts with an unknown compound, resulting in the formation of carbon tetrachloride (CCl4) and hydrochloric acid (HCl). We need to determine the missing reactant.

Identify the missing species by using the conservation of mass

According to the conservation of mass, the total mass of the reactants must be equal to the total mass of the products. From the equation, we can see that the missing species must have chlorine atoms. Since CH4 is a hydrocarbon, it will react with a halogen to form a halocarbon and hydrogen halide. The most suitable candidate for the missing reactant here is chlorine gas (Cl2).

Balance the equation

Now we have the complete equation: \(CH_4 + 4 Cl_2 \rightarrow CCl_4 + 4 HCl\). This chemical equation is balanced in terms of the number of atoms for each element on the reactant and product sides.

Key concepts

Conservation of Mass

In the study of chemistry, the conservation of mass is a fundamental principle. It dictates that mass cannot be created or destroyed in a chemical reaction. This means the total mass of the reactants—what you start with—must equal the total mass of the products—what you end with.

For a practical example, consider a simple chemical equation like the one from the exercise:

• Before the reaction: Sodium hydroxide (NaOH) and sulfuric acid (H2SO4) are separate reactants.
• After the reaction: Sodium hydrogen sulfate (NaHSO4) and water (H2O) are formed.

Each type of atom present in the reactants must be accounted for in the products, keeping the total mass the same on both sides of the equation.

This principle helps chemists ensure chemical equations are balanced, accurately representing the conservation of atoms throughout the reaction process.

Chemical Reactions

Chemical reactions are processes where substances change into new substances with different properties. In these reactions, the bonds between atoms are broken and new ones are formed, leading to new products. Every chemical equation represents a chemical reaction, showing the reactants transforming into products.

For example, let's consider the transformation in the exercise where phosphorus trichloride (PCl3) reacts with water (H2O). Here:

• The reactants are PCl3 and H2O.
• Through the reaction, new products—phosphorous acid (H3PO3) and hydrochloric acid (HCl)—are formed.

One notable aspect of chemical reactions is how they obey the conservation of mass. The number of each type of atom remains constant overall, although they may rearrange into new compounds.

This rearrangement is shown clearly in balanced chemical equations, which depict Reactants \(\rightarrow\) Products.

Reactants and Products

In any chemical reaction, there are starting substances known as reactants, and resulting substances called products. These two groups are linked by a transformation that reconfigures atomic structures.

In the example reaction from the exercise:

• Reactants: Methane (CH4) and chlorine gas (Cl2).
• Products: Carbon tetrachloride (CCl4) and hydrochloric acid (HCl).

The reactants are the substances you begin with, and through the reaction, they are transformed into products. Understanding this transformation helps in predicting the behavior of chemical systems.

The role of a balanced chemical equation is to show this transformation in a condensed and precise manner, ensuring all reactants and resulting products are accounted for. Identifying reactants and products is essential as they define the entire chemical change occurring during the reaction.