Question

Complete and balance each gas evolution reaction. (a) \(\mathrm{HBr}(a q)+\mathrm{NaHCO}_{3}(a q) \longrightarrow\) (b) \(\mathrm{NH}_{4} \mathrm{I}(a q)+\mathrm{KOH}(a q)\) (c) \(\mathrm{HNO}_{3}(a q)+\mathrm{K}_{2} \mathrm{SO}_{3}(a q) \longrightarrow\) (d) \(\mathrm{HI}(a q)+\mathrm{Li}_{2} \mathrm{~S}(a q) \longrightarrow\)

Short answer

(a) HBr + NaHCO3 -> NaBr + H2O + CO2, (b) NH4I + KOH -> KI + H2O + NH3, (c) 2HNO3 + K2SO3 -> 2KNO3 + H2O + SO2, (d) 2HI + Li2S -> 2LiI + H2S.

Step-by-step solution

- Identify the Gas Evolution Reactions

Identify the products based on the combination of reactants that typically produce a gas. In these cases, the reactions will likely produce a gas such as CO2, NH3, SO2, or H2S as one of their products.

- Write the Products for Reaction (a)

The reaction between HBr and NaHCO3 will produce NaBr, H2O, and CO2 gas as the products. The complete balanced reaction is: \( \mathrm{HBr}(aq) + \mathrm{NaHCO}_3(aq) \longrightarrow \mathrm{NaBr}(aq) + \mathrm{H}_2\mathrm{O}(l) + \mathrm{CO}_2(g) \).

- Write the Products for Reaction (b)

The reaction between NH4I and KOH will produce KI, H2O, and NH3 gas as the products. The complete balanced reaction is: \( \mathrm{NH}_4\mathrm{I}(aq) + \mathrm{KOH}(aq) \longrightarrow \mathrm{KI}(aq) + \mathrm{H}_2\mathrm{O}(l) + \mathrm{NH}_3(g) \).

- Write the Products for Reaction (c)

The reaction between HNO3 and K2SO3 will produce KNO3, H2O, and SO2 gas as the products. The complete balanced reaction is: \( 2\mathrm{HNO}_3(aq) + \mathrm{K}_2\mathrm{SO}_3(aq) \longrightarrow 2\mathrm{KNO}_3(aq) + \mathrm{H}_2\mathrm{O}(l) + \mathrm{SO}_2(g) \).

- Write the Products for Reaction (d)

The reaction between HI and Li2S will produce LiI and H2S gas as the products. The complete balanced reaction is: \( 2\mathrm{HI}(aq) + \mathrm{Li}_2\mathrm{S}(aq) \longrightarrow 2\mathrm{LiI}(aq) + \mathrm{H}_2\mathrm{S}(g) \).

Key concepts

Chemical Reaction Balancing

To achieve a complete understanding of chemical reactions, it's essential to start with the balancing of equations. Balancing a chemical equation means ensuring that the number of atoms for each element is the same on both sides of the reaction. This follows the law of conservation of mass which states that matter cannot be created or destroyed in a chemical reaction.

Take the reaction between hydrobromic acid (HBr) and sodium bicarbonate (NaHCO3) for example. Here, the balanced chemical equation is: \[ \mathrm{HBr}(aq) + \mathrm{NaHCO}_3(aq) \longrightarrow \mathrm{NaBr}(aq) + \mathrm{H}_2\mathrm{O}(l) + \mathrm{CO}_2(g) \.\]In this equation, for each substance we count the atoms of each element and balance them on both sides. Thus, we end up with an equal number of hydrogen, bromine, sodium, carbon, and oxygen atoms. This step is crucial as it ensures the reaction is chemically possible and sets the foundation for understanding stoichiometry, yields, and much more in the world of chemistry.

Predicting Reaction Products

Predicting the products of a reaction requires a bit of chemistry know-how and the ability to recognize patterns in reactions. For instance, certain reactants are known to evolve gases when they react with each other. This is significant in the realm of gas evolution reactions.

In the reaction between ammonium iodide (NH4I) and potassium hydroxide (KOH), you predict that the products will include ammonia gas (NH3) along with potassium iodide (KI) and water (H2O): \[ \mathrm{NH}_4\mathrm{I}(aq) + \mathrm{KOH}(aq) \longrightarrow \mathrm{KI}(aq) + \mathrm{H}_2\mathrm{O}(l) + \mathrm{NH}_3(g) \.\]The prediction arises from knowing that ammonium salts and hydroxides often produce ammonia gas upon reacting. The ability to foresee these outcomes is not just about memorizing individual reactions but understanding the properties of reactants and the types of chemical processes that they typically undergo.

Inorganic Chemistry Reactions

Inorganic chemistry explores reactions amongst a diverse group of compounds excluding most carbon-containing molecules. Gas evolution reactions, a category within inorganic chemistry, often involve acids, bases, and salts reacting to form a gaseous product.

For example, the reaction between sulfuric acid (H2SO4) and potassium sulfite (K2SO3) can be anticipated to produce potassium sulfate (K2SO4), water, and sulfur dioxide gas (SO2): \[ 2\mathrm{HNO}_3(aq) + \mathrm{K}_2\mathrm{SO}_3(aq) \longrightarrow 2\mathrm{KNO}_3(aq) + \mathrm{H}_2\mathrm{O}(l) + \mathrm{SO}_2(g) \.\]Each reaction follows specific rules, such as acid-base neutralization, or the reactivity series of metals, to predict the resultant products. These gas evolution reactions are important in industrial processes, environmental chemistry, and are even involved in day-to-day products like baking soda.