Write the balanced chemical equations for the following reactions. (a) Calcium hydroxide + Carbon dioxide \(\rightarrow\) Calcium carbonate + Water (b) Zinc + Silver nitrate \(\rightarrow\) Zinc nitrate + Silver (c) Aluminium + Copper chloride \(\rightarrow\) Aluminium chloride + Copper (d) Barium chloride + Potassium sulphate \(\rightarrow\) Barium sulphate + Potassium chloride

Stoichiometry is a key concept in chemistry that involves the calculation of reactants and products in chemical reactions. It allows chemists to predict the quantities of substances consumed and produced.

When solving stoichiometry problems, start by writing the balanced chemical equation. This gives a clear picture of the molar relationships. For example, in the balanced equation for the reaction between zinc and silver nitrate:
\(\text{Zn} + 2\text{AgNO}_3 \rightarrow \text{Zn(NO}_3\text{)}_2 + 2\text{Ag}\)

The coefficients show that 1 mole of zinc reacts with 2 moles of silver nitrate to produce 1 mole of zinc nitrate and 2 moles of silver. Understanding these relationships is crucial for accurately calculating the amounts needed or produced in a reaction.

Chemical reactions are processes where reactants are transformed into products, involving the breaking and forming of chemical bonds.

Taking the reaction between calcium hydroxide and carbon dioxide as an example:
\(\text{Ca(OH)}_2 + \text{CO}_2 \rightarrow \text{CaCO}_3 + \text{H}_2\text{O}\)

This reaction describes a chemical change where new substances are formed. Calcium hydroxide and carbon dioxide react to form calcium carbonate and water. The reaction is complete when all reactants are converted to products.

To understand chemical reactions thoroughly, one needs to identify the reactants and products, write the respective chemical formulas, and understand the process of how the products result from the reactants.

Balancing chemical equations is essential to respect the Law of Conservation of Mass, which states that matter is neither created nor destroyed.

To balance a chemical equation, ensure that the number of atoms of each element is the same on both sides. Take the reaction between aluminium and copper chloride:
\(\text{2Al} + 3\text{CuCl}_2 \rightarrow 2\text{AlCl}_3 + 3\text{Cu}\)

Start by comparing the number of each type of atom in the reactants and products. Adjust the coefficients to balance each element.

Throughout this process, remember not to change the chemical formulas of the substances, only the coefficients in front of them. This ensures the equation accurately represents the reaction.

Chemical formulas are symbolic representations of molecules or compounds, showing the elements present and their relative proportions.

For example, calcium hydroxide has the chemical formula Ca(OH)\textsubscript{2}. It indicates that each unit contains one calcium atom, two oxygen atoms, and two hydrogen atoms.

In chemical equations, these formulas provide a concise way to represent substances involved in reactions. They also help in determining the reactants and products. For instance, in the equation:
\(\text{BaCl}_2 + \text{K}_2\text{SO}_4 \rightarrow \text{BaSO}_4 + 2\text{KCl}\)

Barium chloride (BaCl\textsubscript{2}) and potassium sulphate (K\textsubscript{2}SO\textsubscript{4}) react to form barium sulphate (BaSO\textsubscript{4}) and potassium chloride (KCl). Understanding the symbols and structure of these formulas is fundamental to grasping the nature of the substances and the chemical processes they undergo.