Problem 78
Question
Write formulas for two salts that (a) contain \(\mathrm{NH}_{4}{\underline{\phantom{xx}}}^{+}\) and are basic. (b) contain \(\mathrm{CO}_{3}^{2-}\) and are basic. (c) contain \(\mathrm{Br}^{-}\) and are neutral. (d) contain \(\mathrm{ClO}_{4}^{-}\) and are acidic.
Step-by-Step Solution
Verified Answer
Question: Provide two examples of salts that fit the following descriptions:
a) Formulas for salts containing NH4+ and are basic.
b) Formulas for salts containing CO3^(2-) and are basic.
c) Formulas for salts containing Br- and are neutral.
d) Formulas for salts containing ClO4- and are acidic.
Answer:
a) 1. Ammonium carbonate (NH4)2CO3
2. Ammonium hydrogen phosphate (NH4)2HPO4
b) 1. Sodium carbonate (Na2CO3)
2. Calcium carbonate (CaCO3)
c) 1. Sodium bromide (NaBr)
2. Potassium bromide (KBr)
d) 1. Ammonium perchlorate (NH4ClO4)
2. Aluminum perchlorate (Al(ClO4)3)
1Step 1: (a) Formulas for salts containing NH4+ and are basic
To find salts containing the ammonium ion (NH4+) that are basic, we need to think of salts formed by the reaction of a strong base with a weak acid. Remember that ammonium salts generally exhibit acidic properties in water because NH4+ can donate a proton. However, if we pair it with a stronger base (a conjugate base of a weak acid), the salt will possess basic properties instead, because the conjugate base will dominate.
Two such examples are:
1. Ammonium carbonate (NH4)2CO3, formed by the reaction of ammonium hydroxide (NH4OH, a weak base) with carbonic acid (H2CO3, an even weaker acid).
2. Ammonium hydrogen phosphate (NH4)2HPO4, formed by the reaction of ammonium hydroxide (NH4OH, a weak base) with phosphoric acid (H3PO4, a weak acid, but stronger than NH4OH)
2Step 2: (b) Formulas for salts containing CO3^(2-) and are basic
Salts containing the carbonate ion (CO3^(2-)) and are basic can be formed by the reaction of a weak acid with a strong base, such as group 1 or group 2 hydroxides. Carbonates generally exhibit basic properties when dissolved in water because they can accept a proton from water to produce bicarbonate ions (HCO3-) and hydroxide ions (OH-).
Two such examples are:
1. Sodium carbonate (Na2CO3, formed by the reaction of sodium hydroxide (NaOH, a strong base) with carbonic acid (H2CO3, a weak acid).
2. Calcium carbonate (CaCO3), formed by the reaction of calcium hydroxide (Ca(OH)2, a strong base) with carbonic acid (H2CO3, a weak acid).
3Step 3: (c) Formulas for salts containing Br- and are neutral
Salts containing the bromide ion (Br-) and are neutral can be formed by a reaction between a strong acid and a strong base. Bromide salts formed from strong acids and bases are neutral because neither ion has notable acid-base properties.
Two such examples are:
1. Sodium bromide (NaBr), formed by the reaction of sodium hydroxide (NaOH, a strong base) with hydrobromic acid (HBr, a strong acid).
2. Potassium bromide (KBr), formed by the reaction of potassium hydroxide (KOH, a strong base) with hydrobromic acid (HBr, a strong acid).
4Step 4: (d) Formulas for salts containing ClO4- and are acidic
Salts containing the perchlorate ion (ClO4-) and are acidic can be formed by the reaction of a strong acid (like perchloric acid, HClO4) with a weak base. It is important to note that perchlorate ion, being the conjugate base of the strongest acid, has no basic properties, but if it's paired with a weak base, the acidic properties of its counterpart in the salt will dominate.
Two such examples are:
1. Ammonium perchlorate (NH4ClO4), formed by the reaction of perchloric acid (HClO4, a strong acid) with ammonium hydroxide (NH4OH, a weak base).
2. Aluminum perchlorate (Al(ClO4)3), formed by the reaction of perchloric acid (HClO4, a strong acid) with aluminum hydroxide (Al(OH)3, a weak base).
Key Concepts
Acid-Base ReactionsSalt SolubilitypH of Salts
Acid-Base Reactions
Understanding acid-base reactions is central to predicting the properties of chemical salts. An acid is a substance that can donate protons (hydrogen ions, H+), while a base is one that can accept them. The reaction between an acid and a base typically results in the formation of a salt and water, in a process known as neutralization.
For example, when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), sodium chloride (NaCl), a neutral salt, is formed along with water (H2O). The equation for this reaction is: \[\text{HCl}(\text{aq}) + \text{NaOH}(\text{aq}) \rightarrow \text{NaCl}(\text{aq}) + \text{H2O}(\text{l})\].
Salt characteristics, such as whether they are acidic, basic, or neutral, depend on the strength of the acids and bases from which they are derived. A neutral salt results from the reaction of a strong acid with a strong base, as seen with sodium bromide (NaBr). If a strong acid reacts with a weak base, the salt will exhibit acidic properties, exemplified by ammonium perchlorate (NH4ClO4). Conversely, a salt formed from a strong base and a weak acid will have basic properties, like sodium carbonate (Na2CO3).
For example, when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), sodium chloride (NaCl), a neutral salt, is formed along with water (H2O). The equation for this reaction is: \[\text{HCl}(\text{aq}) + \text{NaOH}(\text{aq}) \rightarrow \text{NaCl}(\text{aq}) + \text{H2O}(\text{l})\].
Salt characteristics, such as whether they are acidic, basic, or neutral, depend on the strength of the acids and bases from which they are derived. A neutral salt results from the reaction of a strong acid with a strong base, as seen with sodium bromide (NaBr). If a strong acid reacts with a weak base, the salt will exhibit acidic properties, exemplified by ammonium perchlorate (NH4ClO4). Conversely, a salt formed from a strong base and a weak acid will have basic properties, like sodium carbonate (Na2CO3).
Salt Solubility
Salt solubility in water is an important concept as it determines how salts behave in different environments. Solubility is influenced by factors such as temperature, the solvent's polarity, and the salt's ionic lattice energy. Commonly, salts comprised of ions from Group 1 elements or nitrate ions are highly soluble in water.
The solubility of a salt also impacts its ability to conduct electricity when in solution. For instance, sodium chloride (NaCl) is highly soluble and dissociates into its constituent ions, becoming an excellent conductor of electricity in its aqueous form. However, salts like calcium carbonate (CaCO3), although sparingly soluble, have low solubility that leads to the buildup of scale in pipes and boilers.
Understanding the solubility rules can help predict a salt's behavior in a solution, which is crucial in fields such as environmental science, medicine, and chemical engineering.
The solubility of a salt also impacts its ability to conduct electricity when in solution. For instance, sodium chloride (NaCl) is highly soluble and dissociates into its constituent ions, becoming an excellent conductor of electricity in its aqueous form. However, salts like calcium carbonate (CaCO3), although sparingly soluble, have low solubility that leads to the buildup of scale in pipes and boilers.
Understanding the solubility rules can help predict a salt's behavior in a solution, which is crucial in fields such as environmental science, medicine, and chemical engineering.
pH of Salts
The pH of salts is an intriguing aspect of their chemistry, providing insight into whether a salt solution is acidic, basic, or neutral. The pH scale, ranging from 0 to 14, measures how acidic or basic a solution is. A pH of 7 is neutral, values below 7 indicate acidity, and values above 7 indicate basicity.
The pH of a salt solution depends on the acids and bases from which the salt was formed. Salts originating from strong acids and strong bases, such as potassium bromide (KBr), usually result in a neutral pH when dissolved in water. However, if a salt is derived from a strong acid and a weak base, it will typically produce an acidic solution. Conversely, salts from weak acids and strong bases, like ammonium carbonate ((NH4)2CO3), tend to result in basic solutions.
It's vital for students to recognize the relationship between the strength of parent acids and bases and the resulting pH of salt solutions, as this knowledge is applicable in various scientific processes, including chemical manufacturing and environmental monitoring.
The pH of a salt solution depends on the acids and bases from which the salt was formed. Salts originating from strong acids and strong bases, such as potassium bromide (KBr), usually result in a neutral pH when dissolved in water. However, if a salt is derived from a strong acid and a weak base, it will typically produce an acidic solution. Conversely, salts from weak acids and strong bases, like ammonium carbonate ((NH4)2CO3), tend to result in basic solutions.
It's vital for students to recognize the relationship between the strength of parent acids and bases and the resulting pH of salt solutions, as this knowledge is applicable in various scientific processes, including chemical manufacturing and environmental monitoring.
Other exercises in this chapter
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