Chapter 4: Problem 53
Write balanced molecular and net ionic equations for the reactions of (a) manganese with dilute sulfuric acid; (b) chromium with hydrobromic acid; (c) tin with hydrochloric acid; (d) aluminum with formic acid, \(\mathrm{HCOOH}\)
Short Answer
Expert verified
The balanced molecular and net ionic equations for the given reactions are:
(a) Manganese with dilute sulfuric acid:
\(\mathrm{Mn + H_2SO_4 \rightarrow MnSO_4 + H_2}\)
(b) Chromium with hydrobromic acid:
\(\mathrm{2Cr + 6HBr \rightarrow 2CrBr_3 + 3H_2}\)
(c) Tin with hydrochloric acid:
\(\mathrm{Sn + 2HCl \rightarrow SnCl_2 + H_2}\)
(d) Aluminum with formic acid:
\(\mathrm{2Al + 6HCOOH \rightarrow 2Al(HCOO)_3 + 3H_2}\)
Step by step solution
01
Write the unbalanced molecular equation
When manganese (\(\mathrm{Mn}\)) reacts with sulfuric acid (\(\mathrm{H_2SO_4}\)), manganese sulfate (\(\mathrm{MnSO_4}\)) and hydrogen gas (\(\mathrm{H_2}\)) are formed:
\(\mathrm{Mn + H_2SO_4 \rightarrow MnSO_4 + H_2}\)
02
Balance the molecular equation
To balance the equation, we place appropriate coefficients in front of the reactants and products:
\(\mathrm{Mn + H_2SO_4 \rightarrow MnSO_4 + H_2}\) (already balanced)
03
Write the net ionic equation
The net ionic equation only includes species that change their oxidation state in the reaction. Since manganese and hydrogen change their oxidation states, the net ionic equation is the same as the balanced molecular equation:
\(\mathrm{Mn + H_2SO_4 \rightarrow MnSO_4 + H_2}\)
(b) Chromium with hydrobromic acid
04
Write the unbalanced molecular equation
When chromium (\(\mathrm{Cr}\)) reacts with hydrobromic acid (\(\mathrm{HBr}\)), chromium(III) bromide (\(\mathrm{CrBr_3}\)) and hydrogen gas (\(\mathrm{H_2}\)) are formed:
\(\mathrm{Cr + HBr \rightarrow CrBr_3 + H_2}\)
05
Balance the molecular equation
To balance the equation, we place appropriate coefficients in front of the reactants and products:
\(\mathrm{2Cr + 6HBr \rightarrow 2CrBr_3 + 3H_2}\)
06
Write the net ionic equation
The net ionic equation only includes species that change their oxidation state in the reaction. Since chromium and hydrogen change their oxidation states, the net ionic equation is the same as the balanced molecular equation:
\(\mathrm{2Cr + 6HBr \rightarrow 2CrBr_3 + 3H_2}\)
(c) Tin with hydrochloric acid
07
Write the unbalanced molecular equation
When tin (\(\mathrm{Sn}\)) reacts with hydrochloric acid (\(\mathrm{HCl}\)), tin(II) chloride (\(\mathrm{SnCl_2}\)) and hydrogen gas (\(\mathrm{H_2}\)) are formed:
\(\mathrm{Sn + HCl \rightarrow SnCl_2 + H_2}\)
08
Balance the molecular equation
To balance the equation, we place appropriate coefficients in front of the reactants and products:
\(\mathrm{Sn + 2HCl \rightarrow SnCl_2 + H_2}\)
09
Write the net ionic equation
The net ionic equation only includes species that change their oxidation state in the reaction. Since tin and hydrogen change their oxidation states, the net ionic equation is the same as the balanced molecular equation:
\(\mathrm{Sn + 2HCl \rightarrow SnCl_2 + H_2}\)
(d) Aluminum with formic acid
10
Write the unbalanced molecular equation
When aluminum (\(\mathrm{Al}\)) reacts with formic acid (\(\mathrm{HCOOH}\)), aluminum formate (\(\mathrm{Al(HCOO)_3}\)) and hydrogen gas (\(\mathrm{H_2}\)) are formed:
\(\mathrm{Al + HCOOH \rightarrow Al(HCOO)_3 + H_2}\)
11
Balance the molecular equation
To balance the equation, we place appropriate coefficients in front of the reactants and products:
\(\mathrm{2Al + 6HCOOH \rightarrow 2Al(HCOO)_3 + 3H_2}\)
12
Write the net ionic equation
The net ionic equation only includes species that change their oxidation state in the reaction. Since aluminum and hydrogen change their oxidation states, the net ionic equation is the same as the balanced molecular equation:
\(\mathrm{2Al + 6HCOOH \rightarrow 2Al(HCOO)_3 + 3H_2}\)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Net Ionic Equations
Understanding net ionic equations is crucial when studying chemical reactions. A net ionic equation shows only the chemical species that are involved in a reaction and excludes the spectator ions that remain unchanged. This simplifies the reaction down to the core components that actually participate in the chemical change.
For instance, let's consider the reaction between tin and hydrochloric acid, with the balanced molecular equation given as \br\(\mathrm{Sn + 2HCl \rightarrow SnCl_2 + H_2}\). Here, the tin (\br\(\mathrm{Sn}\)) and the hydrogen ions from the acid react to form tin(II) chloride and hydrogen gas. The net ionic equation is the same because all the reactants and products are directly involved and change their oxidation states. Remember, net ionic equations are valuable for understanding the actual chemistry of what's happening in a reaction.
For instance, let's consider the reaction between tin and hydrochloric acid, with the balanced molecular equation given as \br\(\mathrm{Sn + 2HCl \rightarrow SnCl_2 + H_2}\). Here, the tin (\br\(\mathrm{Sn}\)) and the hydrogen ions from the acid react to form tin(II) chloride and hydrogen gas. The net ionic equation is the same because all the reactants and products are directly involved and change their oxidation states. Remember, net ionic equations are valuable for understanding the actual chemistry of what's happening in a reaction.
Oxidation States
The oxidation state, or oxidation number, is a value assigned to an element in a chemical compound that represents its degree of oxidation or loss of electrons. It provides insight into the electron transfer process that occurs during chemical reactions.
For example, in the reaction of aluminum with formic acid, aluminum starts with an oxidation state of 0 in its elemental form and is transformed to an oxidation state of +3 in aluminum formate. Conversely, hydrogen in formic acid changes from an oxidation state of +1 to 0 in hydrogen gas, indicating that aluminum is oxidized while hydrogen is reduced. By comparing the oxidation states before and after the reaction, you can determine which elements are oxidized and reduced, key concepts in redox reactions.
For example, in the reaction of aluminum with formic acid, aluminum starts with an oxidation state of 0 in its elemental form and is transformed to an oxidation state of +3 in aluminum formate. Conversely, hydrogen in formic acid changes from an oxidation state of +1 to 0 in hydrogen gas, indicating that aluminum is oxidized while hydrogen is reduced. By comparing the oxidation states before and after the reaction, you can determine which elements are oxidized and reduced, key concepts in redox reactions.
Reaction with Acids
Reactions with acids are a common type of chemical reaction wherein a metal reacts with an acidic solution to produce a salt and hydrogen gas. The general form of these reactions can be represented by the equation \br\(\mathrm{Metal + Acid \rightarrow Salt + H_2}\).
During these reactions, acids donate hydrogen ions (\br\(\mathrm{H^+}\)) which then bind with the metal atoms to produce molecular hydrogen (\br\(\mathrm{H_2}\)) gas. The remaining ions from the acid combine with the metal to form a salt. For instance, in the reaction of manganese with dilute sulfuric acid, \br\(\mathrm{Mn + H_2SO_4 \rightarrow MnSO_4 + H_2}\), manganese sulfate is the salt formed as a product alongside hydrogen gas.
During these reactions, acids donate hydrogen ions (\br\(\mathrm{H^+}\)) which then bind with the metal atoms to produce molecular hydrogen (\br\(\mathrm{H_2}\)) gas. The remaining ions from the acid combine with the metal to form a salt. For instance, in the reaction of manganese with dilute sulfuric acid, \br\(\mathrm{Mn + H_2SO_4 \rightarrow MnSO_4 + H_2}\), manganese sulfate is the salt formed as a product alongside hydrogen gas.
Chemical Equation Stoichiometry
Stoichiometry is the quantitative aspect of chemical equations—it involves calculating the proportions of reactants and products in chemical reactions. In stoichiometry, balanced equations are essential because they show the exact ratio of molecules and atoms needed for the reactants to fully react and the products to be fully formed.
For example, when balancing the reaction between chromium and hydrobromic acid, you can see that two chromium atoms react with six moles of hydrobromic acid to yield two moles of chromium(III) bromide and three moles of hydrogen gas: \br\(\mathrm{2Cr + 6HBr \rightarrow 2CrBr_3 + 3H_2}\). Balancing chemical equations ensures the conservation of mass and atoms according to the law of conservation of matter and is a fundamental practice in chemistry.
For example, when balancing the reaction between chromium and hydrobromic acid, you can see that two chromium atoms react with six moles of hydrobromic acid to yield two moles of chromium(III) bromide and three moles of hydrogen gas: \br\(\mathrm{2Cr + 6HBr \rightarrow 2CrBr_3 + 3H_2}\). Balancing chemical equations ensures the conservation of mass and atoms according to the law of conservation of matter and is a fundamental practice in chemistry.
