An experimenter attempts to carry out a single replacement reaction between solid potassium and a solution of hydrogen iodide.
Which is more reactive - potassium or hydrogen?
Which of the following equations correctly predicts the products of the reaction?
i. $2 K_{( s )}+2 HI _{( aq )} \rightarrow I _{2( l )}+2 HK _{( aq )}$
ii. $K _{( s)}+ HI _{( aq )} \rightarrow KHI _{( s )}$
iii. $2 K_{( s)}+2 HI _{( aq )} \rightarrow H _{2(g)}+2 KI _{( aq )}$
iv. $K _{( s)}+ HI _{( aq )} \rightarrow$ no reaction
Answer (2)
Potassium is more reactive than hydrogen.
The single replacement reaction between potassium and hydrogen iodide produces potassium iodide and hydrogen gas.
The balanced chemical equation for the reaction is: 2 K ( s ) + 2 H I ( a q ) → 2 K I ( a q ) + H 2 ( g ) .
The correct equation that predicts the products of the reaction is option iii.
b o x e d P o t a ss i u m is more reactive than hydrogen, and option iii is the correct equation.
Explanation
Understanding Reactivity In a single replacement reaction, a more reactive element replaces a less reactive element in a compound. To determine which element is more reactive, we can refer to the activity series of metals.
Identifying the Elements Potassium (K) is an alkali metal located in Group 1 of the periodic table. Alkali metals are known for their high reactivity due to their tendency to lose one electron to achieve a stable electron configuration. Hydrogen (H) is a nonmetal that can also participate in single replacement reactions, particularly in acids.
Comparing Reactivity Based on the activity series, alkali metals like potassium are much more reactive than hydrogen. Therefore, potassium will replace hydrogen in a reaction with hydrogen iodide (HI).
Predicting the Products The general form of the single replacement reaction between potassium and hydrogen iodide is: K ( s ) + H I ( a q ) → K I ( a q ) + H 2 ( g ) Potassium replaces hydrogen in hydrogen iodide, forming potassium iodide and hydrogen gas.
Balancing the Equation To balance the equation, we need two potassium atoms, two hydrogen iodide molecules, two potassium iodide molecules, and one hydrogen molecule: 2 K ( s ) + 2 H I ( a q ) → 2 K I ( a q ) + H 2 ( g )
Identifying the Correct Equation Comparing the balanced equation with the given options, we find that option iii is the correct equation: 2 K ( s ) + 2 H I ( a q ) → H 2 ( g ) + 2 K I ( a q )
Final Answer Therefore, potassium is more reactive than hydrogen, and the correct equation for the reaction is option iii.
Examples
Single replacement reactions are commonly used in various industrial processes, such as the extraction of metals from their ores. For example, a more reactive metal like zinc can be used to extract copper from copper sulfate solution. This principle is also applied in corrosion prevention, where a more reactive metal is used as a sacrificial anode to protect a less reactive metal from corrosion. Understanding single replacement reactions helps in designing and optimizing these processes.
Potassium is more reactive than hydrogen, and during the reaction with hydrogen iodide, it produces potassium iodide and hydrogen gas. The correct equation for this reaction is option iii: 2 K ( s ) + 2 H I ( a q ) → H 2 ( g ) + 2 K I ( a q ) .
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