IMG_6515.jpeg

# Chapter 1: Chemical Reactions and Equations ## 1.1 Chemical Reactions **Chemical Reaction:** Process that transforms chemical substances. - Involve bond breaking and formation to produce new substances. ### Examples of Chemical Reactions 1. **Iron rusting:** $Fe + O_2 + H_2O \rightarr...

# Chapter 1: Chemical Reactions and Equations ## 1.1 Chemical Reactions **Chemical Reaction:** Process that transforms chemical substances. - Involve bond breaking and formation to produce new substances. ### Examples of Chemical Reactions 1. **Iron rusting:** $Fe + O_2 + H_2O \rightarrow Fe_2O_3 \cdot xH_2O$ 2. **Magnesium ribbon burning:** $Mg + O_2 \rightarrow MgO$ 3. **Curdling of milk** 4. **Digestion of food** 5. **Respiration** ### Observations that Help Determine a Chemical Reaction 1. Change in state 2. Change in color 3. Evolution of gas 4. Change in temperature ### Chemical Equations * Represent chemical reactions. * Use chemical symbols and formulas. **Example:** $Mg + O_2 \rightarrow MgO$ * **Reactants:** Substances that participate in a chemical reaction (Left Hand Side - LHS). * **Products:** Substances formed as a result of a chemical reaction (Right Hand Side - RHS). ### Writing Chemical Equations * Write symbols/formulas of reactants on LHS, separated by a plus sign (+). * Write symbols/formulas of products on RHS, separated by a plus sign (+). * Use an arrow ($\rightarrow$) to separate reactants and products. ### Balanced Chemical Equations * Have an equal number of atoms of each element on both sides of the equation. * Follow the law of conservation of mass. **Example:** $Zn + H_2SO_4 \rightarrow ZnSO_4 + H_2$ ### Balancing Chemical Equations 1. Write the unbalanced equation. 2. Count the number of atoms of each element on both sides. 3. Start balancing with the most complex compound. 4. Balance elements one at a time, using coefficients. 5. Verify that the number of atoms of each element is equal on both sides. **Example:** $Fe + H_2O \rightarrow Fe_3O_4 + H_2$ **Steps:** 1. Unbalanced Equation: $Fe + H_2O \rightarrow Fe_3O_4 + H_2$ 2. Count atoms: | Element | LHS | RHS | | ------- | --- | --- | | Fe | 1 | 3 | | H | 2 | 2 | | O | 1 | 4 | 3. Balance Fe: $3Fe + H_2O \rightarrow Fe_3O_4 + H_2$ 4. Balance O: $3Fe + 4H_2O \rightarrow Fe_3O_4 + H_2$ 5. Balance H: $3Fe + 4H_2O \rightarrow Fe_3O_4 + 4H_2$ 6. Balanced Equation: $3Fe + 4H_2O \rightarrow Fe_3O_4 + 4H_2$ ### Physical States * Represented by symbols: (s) - solid, (l) - liquid, (g) - gas, (aq) - aqueous solution. **Example:** $3Fe(s) + 4H_2O(g) \rightarrow Fe_3O_4(s) + 4H_2(g)$ This notation provides additional information about the physical state of each substance in the reaction.