Chapter 4 Pt 1 Chemical Reactions

Which of the following compounds is water soluble? Select the correct answer below: AgCl PbCl2 AgBr KBr

Correct answer: KBr Halides of silver and lead are insoluble, but potassium bromide is soluble.

Which of the following compounds is water insoluble? Select the correct answer below: Na2SO4 MgSO4 K2SO4 PbSO4

Correct answer: PbSO4 Sulfates are typically soluble, but lead sulfate is an exception to this rule, so lead sulfate will form a precipitate.

Which of the following dissolves in water to yield hydronium ions? Select the correct answer below: ions water bases acids

Correct answer: acids Acids dissolve in water to yield hydronium ions.

Complete the acid-base reaction between butyric acid HC4H7O2 and potassium hydroxide KOH. Do not include spectator ions. Do not include phase designations for any of the reactants or products. Be sure to include the charge for any charged species.

Correct answers: HC4​H7​O2​ + OH− → C4​H7​O−2​ + H2​O ​ Butyric acid is a weak acid and potassium hydroxide is a strong base so when they react, the H+ from butyric acid is donated to the hydroxide anion to form water and the buyrate anion. HC4H7O2+K++OH−⟶C4H7O2−+H2O+K+ Removing the spectator ion, potassium, the acid-base reaction becomes: HC4H7O2+OH−⟶C4H7O2−+H2O

Predict the products of the following acid-base reaction. Do not write any coefficients equal to 1.

Correct answers: HCl(aq)+NaOH(aq) → H2​O(l)+NaCl(aq)​ Reactions between Arrhenius acids and bases always produce H2O and an ionic compound. This kind of reaction can be alternatively viewed as a double-displacement reaction. The H+ from the acid and the hydroxide ion OH− from the base combine to yield H2O, while the remaining ions combine to form an ionic compound. Here, Na+ combines with Cl− to yield NaCl. Notice that the entire reaction is occurring in an aqueous environment (i.e., with H2O as the solvent), therefore, the product H2O is in the liquid phase (we typically don't describe water as being aqueous, since that simply means that water is dissolved in water). Therefore, H2O should be written first on the product side. This reaction is balanced with all coefficients having a value of 1.

Consider the following chemical equation. C2H6+O2→CO2+H2O What will be the coefficient forCO2in the balanced equation? Type your answer as a whole number. The balanced equation will have all coefficients as whole numbers.

Correct answers:4​ First, write the unbalanced equation: C2H6+O2→CO2+H2O To balance H, add 3 in front of H2O C2H6+O2→CO2+3 H2O To balance C, add 2 in front of CO2: C2H6+O2→2 CO2+3 H2O To balance O, add 3.5 in front of O2: C2H6+3.5 O2→2 CO2+3 H2O Chemical equations are not allowed to have fractions as coefficients. Multiply all coefficients by 2 in order to them be whole numbers. 2 C2H6+7 O2→4 CO2+6 H2O The equation is balanced. Therefore, the coefficient for CO2 in the balanced equation is 4.

Which of the following carbonate compounds is soluble in water? Select the correct answer below: Ag2CO3 CaCO3 (NH4)2CO3 PbCO3

Correct answer: (NH4)2CO3 Ionic compounds containing the carbonate ion are mostly insoluble with the exception of the carbonates of group 1 metal cations and the ammonium ion. Therefore, of the given choices, only ammonium carbonate will be soluble.

Question A reaction is shown. 4 F e plus 3 O subscript 2 forms 2 F e subscript 2 O subscript 3. Using the chemical equation provided, identify which of the following are the coefficients of the reactants. Select all that apply: 7 4 3 2

Correct answer: 4 3 The coefficients are the whole numbers to the left of compounds, and the reactants are to the left of the arrow. In this reaction, the coefficients of the reactants are 4 and 3.

Using the chemical equation provided, identify which of the following are the coefficients of the reactants. 4Fe+3O2⟶2Fe2O3 Select all that apply: 7 4 3 2

Correct answer: 4 3 The coefficients are the whole numbers to the left of compounds, and the reactants are to the left of the arrow. In this reaction, the coefficients of the reactants are 4 and 3.

Assuming two molecules of (H2O) are produced in the balanced reaction equation below, how many hydrogen atoms are involved? 2 H2+O2→2 H2O Select the correct answer below: 1 2 4 8

Correct answer: 4 Four hydrogen atoms are involved in this reaction. On the reactants side, these take the form of two hydrogen molecules, which contain two hydrogen atoms per molecule for a total of four, and on the products side, they take the form of the four hydrogen atoms contained in the two water molecules, two per molecule.

Which of the following hydroxide compounds are insoluble? Al(OH)3 Ba(OH)2 KOH Mg(OH)2 NaOH

Correct answer: Al(OH)3 Mg(OH)2 Ionic compounds containing the hydroxide ion are mostly insoluble with the exception of the hydroxides of group 1 metal cations and barium hydroxide. Therefore, of the given choices, only aluminum hydroxide and magnesium hydroxide will form precipitates.

Which of the following compounds would form a precipitate in solution? Select the correct answer below: LiNO3 AlPO4 CsBr RbHCO3

Correct answer: AlPO4 Phosphates are typically insoluble, and aluminum is not an exception to this rule.

For the following chemical equation: BaBr2(aq)+H2SO4(aq)→BaSO4(s)+2HBr(aq) which will NOT be involved in the net ionic equation? Select the correct answer below: Ba2+(aq) Br−(aq) SO2−4(aq) BaSO4(s)

Correct answer: Br−(aq) As the bromide ion is not involved in generating the precipitate, it will be a spectator ion, and therefore does not appear in the net ionic equation.

The solubility of which of the following compounds could NOT be analyzed using the solubility rules? Select the correct answer below: Ca(NO3)2 AgBr CaCO3 CCl4

Correct answer: CCl4 Carbon tetrachloride is not an ionic compound, so its solubility in water cannot be determined by the solubility rules.

What is occurring in the following unbalanced reaction: ClO−3→ClO2 Select the correct answer below: Chlorine is oxidized. Chlorine is reduced. Oxygen is oxidized. Oxygen is reduced.

Correct answer: Chlorine is reduced. The chlorine atom goes from an oxidation number of +5 to +4, so it has been reduced. Oxygen has an oxidation number of −2 in both compounds, so it is neither oxidized nor reduced.

Identify which of the following is soluble in water. Select the correct answer below: CsF BaSO4 Mg(OH)2 MnS

Correct answer: CsF Cesium fluoride is soluble according to the solubility rule that all compounds of group IA elements are soluble (Cs).

Which of the following compounds is NOT water soluble? Select the correct answer below: NaOH Fe(OH)3 Ba(OH)2 KOH

Correct answer: Fe(OH)3 Hydroxides of group one metals as well as barium are soluble, but hydroxides of transition metals are insoluble.

Which of the following acts as a reductant in the following reaction? H2(g)+Cl2(g)⟶2HCl(g) Select the correct answer below: H2(g) Cl2(g) HCl(g) None of the above

Correct answer: H2(g) The reductant or reducing agent is the species that gets oxidized during the course of the reaction. H2 and Cl2 both start with oxidation numbers of 0. In HCl, hydrogen has an oxidation number of +1, and chlorine has an oxidation number of −1. Therefore, H2 is the reducing agent.

Which of the following dissolves in water to yield hydronium ions? Select all that apply. Select all that apply: NaCl HBr HNO3 HI

Correct answer: HBr HNO3 HI HBr,HNO3, and HI are strong acids: each of these will donate an acidic proton to water to generate hydronium in solution. NaCl will also dissolve in water but has no acidic protons, and thus will produce no hydronium ions in solution.

Write out the (balanced) chemical equation for the reaction that occurs when hypochlorous acid, a weak acid, reacts with water. Select the correct answer below: HOCl(aq)+H3O+(aq)⟶OCl−(aq)+H2O+(l) HOCl(aq)+H2O(l)⇌OCl−(aq)+H3O+(aq) ClO−(aq)+H2O(l)⇌OCl−(aq)+H2O+(aq) Cl2(aq)+H2O(l)⇌Cl−(aq)+H3O+(aq)

Correct answer: HOCl(aq)+H2O(l)⇌OCl−(aq)+H3O+(aq) The two reactants are provided: HOCl and H2O. Since the substance is reported to be an acid, its reaction with water will involve the transfer of H+ from HOCl to H2O to generate hydronium ions, H3O+ and hypochlorite ions, OCl−. HOCl(aq)+H2O(l)⇌OCl−(aq)+H3O+(aq) A double-arrow is appropriate in this equation because it indicates that an equilibrium will result.

Which species is being reduced in the following reaction: 3Hg2++2Fe→3Hg+2Fe3+ Select the correct answer below: Hg2+ Fe Hg Fe3+

Correct answer: Hg2+ The mercury 2+ ion is reduced to neutral mercury, which means the oxidation number goes from +2 to 0, which is a reduction.

An aqueous solution contains the following ions: Cl−, F−, HCO−3, Mg2+, and NH+4. Is a precipitate likely to form? If so, give the formula of the precipitate. Select the correct answer below: Mg(HCO3)2 MgF2 NH4F No precipitate will form.

Correct answer: MgF2 According to the solubility rules, fluorides of group 2 metal cations will form precipitates. Since magnesium is in group 2, an alkaline earth metal, MgF2, will precipitate in this solution.

Predict the result of mixing the following and determine whether precipitation is expected: NaOH(aq)+AgNO3(aq) Select the correct answer below: AgOH2(aq)+Na+, yes NaNO3(aq)+AgOH(s), no NaNO3(aq)+AgOH(s), yes (AgOH)2(aq)+Na+, no

Correct answer: NaNO3(aq)+AgOH(s), yes The products of this reaction are NaNO3 and AgOH. Because hydroxides are insoluble the reaction will produce precipitation.

Solid nickel reacts with aqueous lead (II) nitrate to form solid lead. What is the net ionic equation of this reaction? Select the correct answer below: Pb2+→NO−+Pb(s) Ni(s)+Pb2++2 NO−3→Pb(s) Ni(s)+Pb2+→Ni2++Pb(s) Ni(s)+Pb2++2 NO−3→Ni2++2 NO−3+Pb(s)

Correct answer: Ni(s)+Pb2+→Ni2++Pb(s) The complete ionic equation of this reaction is shown below. Ni(s)+Pb2++2 NO−3→Ni2++2 NO−3+Pb(s) The nitrate ions are spectator ions, since they are on both the reactant and the product side of the equation, and can be removed from the equation giving us the following.Ni(s)+Pb2+→Ni2++Pb(s)

Which of the following is a balanced chemical equation? Select the correct answer below: Mg+HCl→MgCl2+H2 MgF2+Li2CO3→MgCO3+LiF CH4+2 O2→CO2+H P4+3 O2→2 P2O3

Correct answer: P4+3 O2→2 P2O3 The balanced equation will have equal number of atoms of each element on both sides of the equation. The balanced equation has 4 P and 6 O atoms on each side.

Given C+2H2SO4→CO2+2SO2+2H2O, identify which element is reduced. Select the correct answer below: O C S H

Correct answer: S In this redox reaction, S is reduced because its oxidation number decreases from 6+ to 4+ (it gains electrons).

2Li+S→Li2S is a redox reaction. Identify which of the following is the oxidizing agent and its change in oxidation number. Select the correct answer below: Li is the oxidizing agent, oxidation change from 0 to 2+ S is the oxidizing agent, oxidation change from 0 to 2+ Li is the oxidizing agent, oxidation change from 0 to 2− S is the oxidizing agent, oxidation change from 0 to 2−

Correct answer: S is the oxidizing agent, oxidation change from 0 to 2− S is the oxidizing agent because its oxidation number decreases from 0 to 2−.

Determine how many electrons are either produced or consumed by completing and balancing the following half-reaction in either an acidic or a basic solution. Cl2(g)⟶ClO−2(aq) Select the correct answer below: Three electrons are consumed. Three electrons are produced. Six electrons are consumed. Six electrons are produced.

Correct answer: Six electrons are produced. First, balance the chlorine atoms by giving the chlorite anion a coefficient of 2. Cl2(g)⟶2ClO−2(aq) Next, balance the oxygen atoms by adding H2O molecules. The half-reaction shows four O atoms on the right and none on the left, so add 4H2O(l) to the left side.Cl2(g)+4H2O(l)⟶2ClO−2(aq)Next, balance the hydrogen atoms by adding H+ ions. The half-reaction has eight H atoms on the left side and none on the right, so add 8H+(aq) to the right side.Cl2(g)+4H2O(l)⟶8H+(aq)+2ClO−2(aq)At this point, the charge can be balanced by adding electrons (e−). To do so, find the total charge on each side of the reaction. There are no charged species on the left side, so its total charge is 0. The right side of the reaction has 8H+(aq) and 2ClO−2(aq), for a total charge of +8+(−2)=6+. Since each electron has a charge of 1−, add 6e− to the right side of the equation so that each side will have a total charge of 0.Cl2(g)+4H2O(l)⟶8H+(aq)+2ClO−2(aq)+6e−This gives us the answer to the question, which is that six electrons are produced, since they are on the right side of the equation. Notice that it does not make a difference whether the reaction is assumed to be in an acidic or a basic solution. For a basic solution, the last steps would be to add 8OH−(aq) to both sides of the equation, along with combining and simplifying.Cl2(g)+8OH−(aq)⟶4H2O(l)+2ClO−2(aq)+6e−Since the same total charge of 8− is added to both sides of the equation, there is no effect on the number of electrons needed to balance the charges. In a basic solution, each side of the completed and balanced half-reaction has a total charge of 8−, but they are still equal.

What occurs in a precipitation reaction? Select the correct answer below: Two soluble substances recombine to form two different soluble substances. A group 1 cation reacts with acetate. Hydroxides of group 1 metal cations react with Ba2+. Soluble substances combine to form a solid that is insoluble in the reaction solution.

Correct answer: Soluble substances combine to form a solid that is insoluble in the reaction solution. A precipitation reaction occurs when two solvated (usually aqueous) ions combine to form a solid precipitate.

An acid-base reaction occurs when: Select the correct answer below: a neutron is transferred from one molecule to another an electron is transferred from one molecule to another a proton is transferred from one molecule to another none of the above

Correct answer: a proton is transferred from one molecule to another An acid-base reaction occurs when a proton is transferred from one molecule to another.

A precipitate is: Select the correct answer below: an ionic solid water insoluble of neutral charge all of the above

Correct answer: all of the above As a neutral ionic solid that does not dissociate in solution, all of the above characteristics are true of precipitates.

Carbonates are typically insoluble, but one exception would be a carbonate containing what kind of cation? Select the correct answer below: ammonium a transition metal a group two metal lead

Correct answer: ammonium The ammonium ion or group one metal ions constitute the exceptions for carbonate insolubility, so of the options, ammonium carbonate will be the only water soluble compound.

Which of the following is a typical characteristic of acids? an acid donates a proton an acid donates an electron an acid accepts a proton an acid accepts an electron

Correct answer: an acid donates a proton As they are commonly defined, acids are proton (H+) donors while bases are proton acceptors

Which type of anion will typically result in an insoluble compound? Select the correct answer below: chromate bicarbonate chlorate acetate

Correct answer: chromate Chromates will be insoluble except when combined with group one metal cations or the ammonium ion.

The type of equation that shows only the chemistry that occurs in an aqueous solution of ions is called a: Select the correct answer below: molecular equation complete ionic equation net ionic equation chemical reaction

Correct answer: net ionic equation A net ionic equation disregards the ions that simply sit in solution and instead lists the particles that interact to form a new insoluble compound.

The __________ of an atom or molecule __________ when it undergoes reduction. Select the correct answer below: oxidation number, increases oxidation number, decreases charge, increases charge, decreases

Correct answer: oxidation number, decreases The oxidation number of an atom or molecules decreases when it undergoes reduction.

In redox reactions, the species that is reduced is also the _________. (Select all that apply) Select all that apply: oxidizing agent reducing agent reductant oxidant

Correct answer: oxidizing agent oxidant In redox reactions, the species that is reduced is also the oxidizing agent or oxidant.

In redox reactions, the reactant that is oxidized is also called the _________. Select all that apply: oxidizing agent reducing agent reductant oxidant

Correct answer: reducing agent reductant In the reaction of 2Na(s)+Cl2(g)→2NaCl(s), sodium is oxidized and chlorine undergoes reduction. Viewed from a more active perspective, sodium functions as a reducing agent (reductant) since it provides electrons to (or reduces) chlorine. Likewise, chlorine functions as an oxidizing agent (oxidant) as it effectively removes electrons from (oxidizes) sodium.

In a chemical equation, the number of atoms of a particular element that are present in a substance is indicated by a: Select the correct answer below: coefficient forward arrow plus sign subscript

Correct answer: subscript Subscripts indicate how many atoms of a particular element are present in a substance

If precipitation is not expected from a reaction, which of the following is indicated? Select the correct answer below: precipitation is not related to the solubility of a reaction the products are insoluble the products are soluble there is not enough information to answer this question

Correct answer: the products are soluble If precipitation is not expected from a reaction, it is an indication that the products are soluble.

What is the net ionic equation for the following reaction that takes place in water? Mg+H2SO4⟶MgSO4+H2 Include charges on ions.

Correct answers Mg(s) + 2H+(aq) → Mg2+(aq) + H2​(g)​ The complete ionic equation of this reaction is Mg(s)+2H+(aq)+SO2−4(aq)⟶Mg2+(aq)+SO2−4(aq)+H2(g) The sulfate ions are spectator ions and can be removed from the equation, giving usMg(s)+2 H+(aq)→Mg2+(aq)+H2(g)

Aqueous potassium carbonate reacts with aqueous silver nitrate to precipitate silver carbonate. What is the net ionic equation of this reaction? Include charges on ions. Provide your answer below: 2(aq) + CO2−3​(aq) → (s)

Correct answers: The complete balanced equation is: K2CO3(aq)+2 AgNO3(aq)→2 KNO3(aq)+Ag2CO3(s) The complete ionic equation of this reaction is: 2 K+(aq)+CO−23(aq)+2 Ag+(aq)+2 NO−3(aq)→2 K+(aq)+2 NO−3(aq)+Ag2CO3(s) The potassium ions and the nitrate ions are spectator ions and can be removed from the equation giving us the final net ionic reaction:2 Ag+(aq)+CO2−3(aq)→Ag2CO3(s)

Complete and balance the following reaction, assuming an acidic environment, by filling in the missing coefficients and formulas. Ag(s)+NO−3(aq)⟶Ag+(aq)+NO2(g) Do not include the state (phase) information. Include all coefficients, even those equal to 1. Be sure to denote any charges as needed.

Correct answers: 1 Ag+ 1 NO−3​+2H+ → 1 Ag+ + 1 NO2​ + H2​O​ First, write the two half-reactions, balancing Ag and N as needed. In this case, all components are balanced with coefficients of 1. AgNO−3⟶Ag+⟶NO2 Next, add water to the second half-reaction to balance the number of oxygen atoms. AgNO−3⟶Ag+⟶NO2+H2O Add H+ ions to balance the H atoms. AgNO−3+2H+⟶Ag+⟶NO2+H2O Complete each half-reaction by adding electrons to balance the charges. AgNO−3+2H++e−⟶Ag++e−⟶NO2+H2O The total reaction is found by combining the two half-reactions and canceling common species. Free electrons (e−) cannot be actual reactants or products, so they must cancel, which they do in this case without any need to scale either reaction. Combine the two reactions, canceling one e−, which appears on both sides of the equation. Ag+NO−3+2H+⟶Ag++NO2+H2O

Balance the following acid-base reaction. Use a whole number, and make sure to enter a 1 if one of the given compound is needed.

Correct answers: 2KOH+H2​CO3​→2H2​O+K2​CO3​​ We can employ our usual method of counting the number of atoms on each side of the equation for each element. However, we can simplify the process in this case because polyatomic ions, such as the carbonate ion CO2−3 or the hydroxide ion OH−, stay as a chemical unit throughout such reactions. The number of H+ and OH− ions on the left side must match in order to create an exact number of water molecules as products. This observation guides our balancing of acid-base reactions such as this one. There are 2OH− ions on the left side (since there are 2KOH molecules) and 2H+ ions from H2CO3. These combine to form 2HOH or H2O molecules. Therefore, the coefficient in front of H2O should have the value of 2. All other elements and polyatomic ions are appropriately balanced at this point. The balanced equation is shown below. 2KOH+H2CO3⟶2H2O+K2CO3

Fill in the blanks with the coefficients for the balanced version of the following chemical equation: Na+H2O→NaOH+H2 Enter all coefficients as whole numbers, including coefficients of 1. Provide your answer below: $$Na+H2​O→NaOH+H2​

Correct answers: 2Na+2H2​O→2NaOH+1H2​​ First, write the unbalanced equation: Na+H2O→NaOH+H2 To balance H, add 2 in front of the H2O: Na+2H2O→NaOH+H2 To balance O, and H again, put a 2 in front of the NaOH: Na+2H2O→2NaOH+H2 To balance Na, put a 2 in front of the Na: 2Na+2H2O→2NaOH+H2 The equation is balanced.

The following reaction is the precipitation reaction between aqueous solutions of calcium nitrate and potassium carbonate. Ca(NO3)2(aq)+K2CO3(aq)⟶2KNO3(aq)+CaCO3(s) Write the net ionic equation for the reaction. Be sure to Include the charges for any ions in the equation. Do not include state symbols (aq, s, etc) in your answer. Use the reaction arrow symbol to separate reactants from products.

Correct answers: Ca2++CO2−3​ → CaCO3​​ A net ionic equation includes only the reactants and products that change during a reaction. In this case, it is only the reactants and products that directly participate in the precipitation. Recall that common compounds containing the potassium ion K+ and the nitrate ion NO−3 are always soluble. The chemical equation can be rewritten in ionic form as shown. Ca2+(aq)+2NO−3(aq)+2K+(aq)+CO2−3(aq)⟶CaCO3(s)+2NO−3(aq)+2K+(aq) Notice that the K+ and NO−3 ions are the same on both sides of the equation. They are the spectator ions. When they are removed, the net ionic equation remains. Ca2+(aq)+CO2−3(aq)⟶CaCO3(s)

Write and balance the half-reaction for the formation of perchlorate ClO−4 from hypochlorite ClO− in the presence of an aqueous acid. Use e− to represent the formula of an electron. Do NOT include the state (phase) information. Be sure to denote any charges as needed.

Correct answers: ClO−+3H2​O → ClO−4​+6H++6e−​ First, write the half-reaction with the given reactant and product, balancing Cl as needed. In this case, the Cl atoms are balanced with coefficients of 1. ClO−⟶ClO−4 Next, add water to the half-reaction as needed to balance the number of oxygen atoms. ClO−+3H2O⟶ClO−4 Add H+ ions to balance the H atoms. ClO−+3H2O⟶ClO−4+6H+ Complete the half-reaction by adding electrons to balance the charges. ClO−+3H2O⟶ClO−4+6H++6e−

When aqueous solutions of NaCl and AgNO3 are mixed, a reaction occurs that produces NaNO3(aq) and AgCl(s). What is the net ionic equation for this reaction? Be sure to include the charges for all ions in the equation.

Correct answers: Cl−(aq) + Ag+(aq) → AgCl(s)​ First, begin by identifying formulas for the reactants and products and arranging them properly in balanced chemical equation form: NaCl(aq)+AgNO​3(aq)⟶NaNO​3​(aq)+AgCl(s) The dissolved ionic compounds can then be represented as dissociated ions to yield the complete ionic equation: Na+(aq)​+Cl​−(aq)+​​Ag+(aq)​​+NO​−3​(aq)⟶Na+(aq)+NO​3​−(aq)​​+AgCl(s) Finally, identify the spectator ion(s), and remove them from each side of the equation to generate the net ionic equation: Cl−(aq)+Ag+(aq)⟶AgCl(s)

Determine the unknown products for the following acid-base reaction. Use coefficients to balance the reaction, do not include coefficients of 1. Do not include phase labels.

Correct answers: H2​SO4​+2NaOH → Na2​SO4​+2H2​O​ Reactions between Arrhenius acids and bases always produce H2O and an ionic compound. This kind of reaction can be alternatively viewed as a double-displacement reaction. The H+ from the acid and the hydroxide ion OH− from the base combine to yield H2O, while the remaining ions combine to form an ionic compound. Here, two Na+ ions combine with SO2−4 to yield Na2SO4. A coefficient of 2 is needed for water to balance the equation. Therefore, the chemical reaction is written as H2SO4+2NaOH⟶Na2SO4+2H2O

Balance the following acid-base reaction. Use a whole number, and make sure to enter a 1 if one of the given compound is needed.

Correct answers: H2​SO4​+Mg(OH)2​→2H2​O+MgSO4​​ We can employ our usual method of counting the number of atoms on each side of the equation for each element. However, we can simplify the process in this case because polyatomic ions, such as the sulfate ion SO2−4 or the hydroxide ion OH−, stay as a chemical unit throughout such reactions. The number of H+ and OH− ions on the left side must match in order to create an exact number of water molecules as products. This observation guides our balancing of acid-base reactions such as this one. There are 2OH− ions on the left side (since there is 1Mg(OH)2 molecule) and 2H+ ions from H2SO4. These combine to form 2HOH or H2O molecules. Therefore, the coefficient in front of H2O should have the value of 2. All other elements or polyatomic ions are appropriately balanced at this point. The balanced equation is shown below. H2SO4+Mg(OH)2⟶2H2O+MgSO4

Balance the following acid-base reaction. Use a whole number, and make sure to enter a 1 if one of the given compound is needed.

Correct answers: HBr+CsOH→H2​O+1CsBr​ We can employ our usual method of counting the number of atoms on each side of the equation for each element. However, we can simplify the process in this case because polyatomic ions, such as the hydroxide ion OH−, stay as a chemical unit throughout such reactions. The number of H+ and OH− ions on the left side must match in order to create an exact number of water molecules as products. This observation guides our balancing of acid-base reactions such as this one. There is 1OH− ion on the left side (since there is 1CsOH molecule) and 1H+ ion from HBr. These combine to form 1HOH or H2O molecule. Therefore, the coefficient in front of H2O should have the value of 1, as indicated. There is 1 cesium atom on the left side, and 1 on the right if we assume the missing coefficient is 1. There is 1 bromine atom on the left side, and 1 on the right if we assume the missing coefficient is 1. Therefore, a coefficient of 1 in front of the CsBr molecule yields a completely balanced equation, shown below. HBr+CsOH⟶H2O+CsBr

Write the acid-base reaction between the weak base ammonia NH3 and the strong acid hydrobromic acid HBr. Be sure to include the charges on any ions in the equation. If the charge is +1 or -1, only include the + or the - superscript, not the number 1. Please write the charges as a superscript. Do NOT include state phases in your answer.

Correct answers: NH3​+HBr → NH+4​+Br−​ Ammonia is a weak base and hydrobromic acid is a strong acid so when they react, the H+ from HBr will be transferred to NH3 producing NH+4 and Br−

Write and balance the half-reaction for the oxidation of white phosphorous P4 to the phosphate ion PO3−4 in a basic solution. Use e− to represent the formula of an electron. Do NOT include the state (phase) information. Do NOT write out coefficients that are equal to 1. Be sure to denote any charges as needed.

Correct answers: P4​ + 32 OH− → 16 H2​O + 4 PO3−4​ + 20e−​ First, write the half-reaction with the given reactant and product, balancing P atoms by giving the phosphate a coefficient of 4. P4⟶4PO3−4 Next, add water to the half-reaction as needed to balance the number of oxygen atoms. P4+16H2O⟶4PO3−4 Add H+ ions to balance the H atoms. P4+16H2O⟶4PO3−4+32H+ Since the half-reaction is occurring in a basic solution, add 32OH− to each side of the equation to eliminate the H+ ions. P4+16H2O+32OH−⟶4PO3−4+32H++32OH− Combine the H+ and OH− ions to form H2O, and cancel the H2O that appears on both sides of the equation. P4+32OH−⟶4PO3−4+16H2O Complete the half-reaction by adding electrons to balance the charges. P4+32OH−⟶4PO3−4+16H2O+20e−

A precipitate forms when mixing solutions of sodium fluoride (NaF) and lead II nitrate (Pb(NO3)2). Complete and balance the net ionic equation for this reaction by filling in the blanks. The phase symbols and charges on species are already provided.

Correct answers: Pb2+(aq)+2F−(aq) → PbF2​ (s)​ The two possible products for this reaction are NaNO3 and PbF2. The solubility guidelines indicate that PbF2 is insoluble. Na+ and NO−3 ions are both soluble with no exceptions. It is clear that the reaction involves Pb2+ ions and F− ions, and the product is PbF2. The balanced net ionic equation is shown below. Note that there must be two fluoride ions to balance the lead ion. Pb2+(aq)+2F−(aq)⟶PbF2(s)

Complete and balance the following reaction by filling in the missing coefficients. Assume the reaction is occurring in a basic, aqueous solution. CH3CH2OH(aq)+MnO−4(aq)⟶CH3COO−(aq)+MnO2(s) Include all coefficients, even those equal to 1.

Correct answers:$3\ CH_3CH_2OH+\ 4\ MnO_4^-\ \rightarrow\ 1\ OH^-+4\ H_2O+3\ CH_3COO^-+4\ MnO_2$3 CH3​CH2​OH+ 4 MnO−4​ → 1 OH−+4 H2​O+3 CH3​COO−+4 MnO2​​ First, write the two half-reactions, balancing C and Mn as needed. In this case, all components are balanced with coefficients of 1. CH3CH2OHMnO−4⟶CH3COO−⟶MnO2 Next, add water to the half-reactions as needed to balance the number of oxygen atoms. CH3CH2OH+H2OMnO−4⟶CH3COO−⟶MnO2+2H2O Add H+ ions to balance the H atoms. CH3CH2OH+H2OMnO−4+4H+⟶CH3COO−+5H+⟶MnO2+2H2O Since the reaction is occurring in a basic solution, add OH− ions equal to the number of H+ ions on each equation. CH3CH2OH+H2O+5OH−MnO−4+4H++4OH−⟶CH3COO−+5H++5OH−⟶MnO2+2H2O+4OH− Combine the H+ and OH− into H2O and cancel the common H2O on each side of each equation. CH3CH2OH+5OH−MnO−4+2H2O⟶CH3COO−+4H2O⟶MnO2+4OH− Complete each half-reaction by adding electrons to balance the charges. CH3CH2OH+5OH−MnO−4+2H2O+3e−⟶CH3COO−+4H2O+4e−⟶MnO2+4OH− The total reaction is found by combining the two half-reactions and canceling common species. Free electrons (e−) cannot be actual reactants or products, so they must cancel. To ensure that the electrons cancel, multiply the first half-reaction by 3 and the second half-reaction by 4. 3CH3CH2OH+15OH−4MnO−4+8H2O+12e−⟶3CH3COO−+12H2O+12e−⟶4MnO2+16OH− Now combine the two reactions, canceling 15OH−, 8H2O, and 12e−, which appear on both sides of the equation. 3CH3CH2OH+4MnO−4⟶OH−+4H2O+3CH3COO−+4MnO2

Complete and balance the following half reaction. Assume the reaction occurs in basic media. Cl−⟶ClO3− Do not include phase states.

Correct answers:$Cl^-+\ 6OH^-\ \rightarrow\ ClO_3^-\ +\ 3H_2O\ +\ 6\ e^-$Cl−+ 6OH− → ClO−3​ + 3H2​O + 6 e−​ First, balance all elements except oxygen and hydrogen. The half-reaction shows one Cl atom on the left and one Cl atom on the right, so the half reaction is balanced. Balance oxygen atoms by adding H2O molecules. The half-reaction shows three O atoms on the right and none on the left, so three water molecules are added to the left side. Cl−+3H2O⟶ClO3− Balance hydrogen atoms by adding H+ ions. The half-reaction shows 6 H atoms on the left and none on the right, so 6 hydrogen ions are added to the right side. Cl−+3H2O⟶ClO3−+6H+ Add electrons to balance the charge. The charge on the left side of the equation is 1− and the charge on the right side is 5+. Therefore, we must add 6 electrons to the right side of the equation to balance the charge. Cl−+3H2O⟶ClO3−+6H++6e− Because this reaction occurs in basic media, we add 6 OH− ions to each side of the equation. Cl−+3H2O+6OH−⟶ClO3−+6H++6e−+6OH− On the side of the equation containing both H+ and OH− ions, combine these ions to yield water molecules. Cl−+3H2O+6OH−⟶ClO3−+6H2O+6e− Simplify the equation by removing any redundant water molecules. Cl−+6OH−⟶ClO3−+3H2O+6e− Finally, check to see that both the number of atoms and the total charges are balanced.

Write and balance the half-reaction for the reduction of nitrate, NO−3(aq), to nitrogen gas, N2(g), in a basic solution. Use e− to represent the formula of an electron. Do NOT include the state (phase) information. Do NOT write out coefficients that are equal to 1. Be sure to denote any charges as needed.

Correct answers:2NO−3​ + 6H2​O + 10e− → N2​ + 12OH−​ First, write the half-reaction with the given reactant and product, balancing N atoms. 2NO−3⟶N2 Next, add water to the half-reaction as needed to balance the number of oxygen atoms. 2NO−3⟶N2+6H2O Add H+ ions to balance the H atoms. 2NO−3+12H+⟶N2+6H2O Since the half-reaction is occurring in a basic solution, add 12OH− to each side of the equation to eliminate the H+ ions. 2NO−3+12H++12OH−⟶N2+6H2O+12OH− Combine the H+ and OH− ions to form H2O, and cancel the H2O that appears on both sides of the equation. 2NO−3+6H2O⟶N2+12OH− Complete the half-reaction by adding electrons to balance the charges. 2NO−3+6H2O+10e−⟶N2+12OH−

Write the acid-base reaction between the weak base ammonia NH3 and the strong acid hydrochloric acid HCl. Be sure to include the charges on any ions in the equation. If the charge is +1 or -1, only include the + or the - superscript, not the number 1. Do NOT include state phases in your answer.

Correct answers:NH3​+HCl → NH+4​+Cl−​ Ammonia is a weak base and hydrochloric acid is a strong acid so when they react, the H+ from HCl will be transferred to NH3 producing NH+4 and Cl−

What is the coefficient for O2 in the balanced version of the following chemical equation: C2H4+O2→CO2+H2O Your answer should be a whole number.

First, write the unbalanced equation: C2H4+O2→CO2+H2O To balance C and H, add 2 in front of CO2 and 2 in front of H2O: C2H4+O2→2 CO2+2 H2O To balance O, add 3 in front of O2: C2H4+3 O2→2 CO2+2 H2O The equation is balanced. The coefficient in front of O2is 3.

What kind of compound will generate the most hydroxide ions in solution? Select the correct answer below: strong acid strong base weak acid weak base

orrect answer: strong base Bases produce hydroxide ions in aqueous solution, and the stronger the base is, the more of them that will be generated.