Define Hess's Law and Gay-Lussac's Law. Name a basic gas prepared in the lab and list its reagents. Name the reagent used to prepare ethyne gas and write its balanced chemical equation.

14. a) Hess's Law of Constant Heat Summation states that:

$$\boxed{\text{The total enthalpy change for a chemical reaction is the same, regardless of the pathway or number of steps taken to convert reactants to products, as long as the initial and final conditions are the same.}}$$

b) Gay-Lussac's Law (Pressure-Temperature Law) states that:

$$\boxed{\text{For a fixed mass of gas at constant volume, the pressure of the gas is directly proportional to its absolute temperature.}}$$

15. The name of a basic gas is:

    $$\boxed{\text{Ammonia (NH}_3)}$$

    Reagents used to prepare it in the laboratory are:

    $$\boxed{\text{An ammonium salt (e.g., ammonium chloride, NH}_4\text{Cl) and a strong base (e.g., calcium hydroxide, Ca(OH)}_2)}$$

16. The reagent used to prepare ethyne gas ($\text{C}_2\text{H}_2$) in the laboratory is:

    $$\boxed{\text{Calcium carbide (CaC}_2\text{) and water (H}_2\text{O})}$$

    The balanced chemical equation is:

    $$\boxed{\text{CaC}_2\text{(s)} + 2\text{H}_2\text{O(l)} \to \text{C}_2\text{H}_2\text{(g)} + \text{Ca(OH)}_2\text{(aq)}}$$