CHE 100 - Ch. 7
What is the net ionic equation for the following balanced reaction: K2SO4(aq)+BaCl2(aq)→BaSO4(s)+2 KCl(aq)
Ba2+(aq)+SO2−4(aq)→BaSO4(s) The complete ionic equation of this reaction is 2K+(aq)+SO2−4(aq)+Ba2+(aq)+2Cl−(aq)→BaSO4(s)+2 K+(aq)+2 Cl−(aq) The chloride and the potassium ions are spectator ions and can be removed from the equation, giving us Ba2+(aq)+SO2−4(aq)→BaSO4(s)
Digestion of proteins in the stomach is an example of what?
A chemical change. Digestion is an example of a chemical change because the chemical composition of the proteins changes.
What is the type of reaction involved in the following equation? Al(s)+Fe2O3(s)⟶2Fe(s)+Al2O3(s)
Displacement reaction In this reaction, atoms of aluminum replace atoms of iron in the compound with oxygen ions. There are two cations involved, Al3+ and Fe3+, but only one anion, O2−, which remains part of the compound in both the reactant and the product. Rather than forming a compound with a different anion, each cation has its corresponding neutral metal on the opposite side of the reaction arrow. This is a displacement reaction.
Which of the following compounds is NOT water soluble?
Fe(OH)3 According to the solubility rules hydroxides of group one metals as well as barium are soluble, but hydroxides of transition metals are insoluble.
An equation that explicitly represents all dissolved ions is known as a(n):
complete ionic equation An equation that explicitly represents all dissolved ions is known as a complete ionic equation.
Which ions are involved in the net ionic equation?
only the ions that stick together to form the precipitate
Balance this equation: HCl + NH3 -> NH4Cl
1 HCl + 1 NH3 -> 1 NH4Cl First, write the unbalanced equation. HCl+NH3⟶NH4Cl The equation is balanced with 1 as the coefficient for all reactants and products. 1HCl+1NH3⟶1NH4Cl Element Reactants Products Balanced? H (1×1)+(1×3)=4 1×4=4 4=4, yes Cl 1×1=1 1×1=1 1=1, yes N 1×1=1 1×1=1 1=1, yes
The following equation 2C8H18(l)+25O2(g)⟶16CO2(g)+18H2O(g) is an example of
a chemical change (combustion reaction). This is an example of a combustion reaction. The hallmark of such a reaction is the presence of oxygen gas as a reactant and the formation of carbon dioxide and water.
What gaseous product is liberated in gas evolution reactions involving sulfides?
H2S(g) Sulfides generate H2S(g) when involved in gas evolution reactions. Ammonium compounds liberate NH3 gas. Sulfites and bisulfite compounds liberate SO2 gas. FEEDBACK
Which of the following reactions is stoichiometrically equivalent to the reaction shown below? Pb(OH)4+2H2SO4→Pb(SO4)2+4H2O
2Pb(OH)4+4H2SO4→2Pb(SO4)2+8H2O The given equation has a coefficient ratio of 1:2→1:4. Answer B maintains this ratio with 2:4→2:8, which reduces to 1:2→1:4.
All of the following are typically components of soluble compounds EXCEPT
a phosphate ion (PO3−4) Phosphates are typically insoluble, while all of the other ions listed generally form soluble compounds.
How did we know PbI2 would be the precipitate that forms? Choose the best answer.
(i think?) From the solubility rules, lead(II) iodide is insoluble in water or From the solubility rules, lead(II) iodide is soluble in water From the solubility rules, potassium nitrate is soluble in water From the solubility rules, potassium nitrate is insoluble in water
Identify which of the following is soluble in water.
CsF Cesium fluoride is soluble according to the solubility rule that all compounds of group 1 elements are soluble (Cs). While compounds containing sulfate ions are typically soluble, solubility rules state that an exception is BaSO4. Compounds containing the hydroxide ion are usually not soluble which makes Mg(OH)2 insoluble, and MnS is a metallic sulfide which is also insoluble.
What does an "(s)" as a phase mean in a chemical equation?
insoluble solid
Substances on the same side of a chemical equation are separated by a:
plus sign Substances that are on the same side of an equation are separated by plus signs. This indicates that they are both reactants or products, but that they are distinct, separate substances.
You can cross off all of the ______________ in the complete ionic equation to get the net ionic equation.
spectator ions
What is the correct chemical name of this precipitate?
lead(II) iodide
What gaseous product will be liberated in gas evolution reactions with sulfites and bisulfites?
SO2 Sulfites and bisulfites generate SO2 gas when involved in gas evolution reactions. Ammonium compounds liberate NH3 gas. Sulfide compounds liberate H2S(g) gas.
Which of the following can be characterized as a chemical change?
- food digestion by a human - the combustion of ethanol When we digest food, it is a complicated process with a number of chemical reactions occurring. A combustion reaction is also a chemical change.
Predict the result of mixing the following and determine whether precipitation is expected: 2 KI(aq)+Pb(NO3)2(aq)
2 KNO3(aq)+PbI2(s), yes Because this is a double replacement reaction, the products of the reaction are KNO3 and PbI2. According to the solubility rules, halides and nitrates are typically soluble. However, lead (II) iodide is an exception to this rule and will be insoluble, thus producing a precipitate.
Hydrogen peroxide, H2O2, can undergo spontaneous decomposition into water H2O and oxygen O2. Write the balanced chemical reaction with the simplest whole number coefficients.
2H2O2 -> 2H2O + O2 A decomposition reaction means that a single reactant breaks down into multiple products. In this case, the two products are water and oxygen. The number of hydrogen and oxygen atoms on both sides of the equation must be balanced. The completed reaction is shown below. 2H2O2⟶2H2O+O2
Many metals undergo a single displacement reaction with hydrogen chloride (a strong acid, HCl). One example is magnesium, Mg. The products are hydrogen gas, H2, and magnesium chloride, MgCl2. Write the balanced single displacement reaction with the simplest whole number coefficients.
2HCl + Mg -> MgCl2 + H2 A single displacement reaction has the form AB+C→AC+B, where B and C swap places. For the given reactants, A is chlorine, B is hydrogen, and C is magnesium. The number of magnesium, chlorine, and hydrogen atoms on both sides of the equation must be balanced. The completed reaction is shown below. Mg+2HCl⟶MgCl2+H2
Aqueous potassium carbonate reacts with aqueous silver nitrate to precipitate silver carbonate. What is the complete ionic equation of this reaction?
2K+(aq)+CO2−3(aq)+2Ag+(aq)+2NO−3(aq) ⟶2K+(aq)+2NO−3(aq)+Ag2CO3(s) The balanced reaction as described can be written K2CO3(aq)+2AgNO3(aq)⟶2KNO3(aq)+Ag2CO3(s) This form of the reaction is called the molecular form, which is distinct from the ionic forms of the reaction, so the third choice is incorrect. The three aqueous species in the reaction are electrolytes, and actually exist in solution as dissociated ions, so writing them as separate ions gives the complete ionic equation: 2K+(aq)+CO2−3(aq)+2Ag+(aq)+2NO−3(aq) ⟶2K+(aq)+2NO−3(aq)+Ag2CO3(s) This is the correct answer (and the first choice). The second choice is called the net ionic equation, and results from eliminating the spectator ions (those ions that are present on both sides of the complete ionic equation).
Determine a balanced equation for the reaction of molecular nitrogen (N2) and oxygen (O2) to form dinitrogen pentoxide.
2N2+5O2→2N2O5 First, write the unbalanced equation: N2+O2→N2O5 Next, count the number of each type of atom present in the unbalanced equation. Element Reactants Products Balanced? N 1×2=2 1×2=2 2=2, yes O 1×2=2 1×5=5 2≠5, no Though nitrogen is balanced, changes in coefficients are needed to balance the number of oxygen atoms. To balance the number of oxygen atoms, a reasonable first attempt would be to change the coefficients for the O2 and N2O5 to integers that will yield 10 O atoms (the least common multiple for the O atom subscripts in these two formulas). Element Reactants Products Balanced? N 1×2=2 2×2=4 2≠4, no O 5×2=10 2×5=10 10=10, yes The N atom balance has been upset by this change; it is restored by changing the coefficient for the reactant N2 to 2. 2N2+5O2→2N2O5 Element Reactants Products Balanced? N 2×2=4 2×2=4 4=4, yes O 5×2=10 2×5=10 10=10, yes The numbers of N and O atoms on either side of the equation are now equal, and so the equation is balanced.
What is the coefficient for O2 in the balanced version of the following chemical equation: C2H4+O2→CO2+H2O
3 First, write the unbalanced equation: C2H4+O2→CO2+H2O To balance C and H, add a coefficient of 2 in front of CO2 and a coefficient of 2 in front of H2O: C2H4+O2→2 CO2+2 H2O To balance O, add a coefficient of 3 in front of O2: C2H4+3 O2→2 CO2+2 H2O The equation is now balanced. The coefficient in front of O2 is 3.
Hydrochloric acid dissolves solid aluminum hydroxide. What is the net ionic equation of this reaction?
3 H+(aq)+Al(OH)3(s)→3 H2O(l)+Al3+(aq) The complete ionic equation of this reaction is 3 H+(aq)+3 Cl−(aq)+Al(OH)3(s)→3 H2O(l)+Al3+(aq)+3 Cl−(aq) The chloride ions are spectator ions and can be removed from the equation, giving us 3 H+(aq)+Al(OH)3(s)→3 H2O(l)+Al3+(aq)
Choose the coefficient for SiO2 in the balanced version of the following chemical equation, using only whole numbers: Si2H6+O2→SiO2+H2O .
4 First, write the unbalanced equations: Si2H6+O2→SiO2+H2O To balance Si, add 2 in front of the SiO2: Si2H6+O2→2SiO2+H2O To balance H, put a 3 in front of the H2O: Si2H6+O2→2SiO2+3H2O The right side has 7 oxygens. Write 7/2 in front of O2 to give us 7 oxygens on the left side. Si2H6+7/2O2→2SiO2+3H2O Finally, multiply everything through by 2 to get rid of the fraction: 2Si2H6+7O2→4SiO2+6H2O
Using the chemical equation provided, identify which of the following are the coefficients of the reactants. 4Fe+3O2⟶2Fe2O3
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. The coefficient 2 is a coefficient of the product, not of the reactants.
Which of the following compounds would form a precipitate in solution?
AlPO4 Phosphates are typically insoluble, and aluminum is not an exception to this rule. Compounds containing group 1 elements and halide ions are typically soluble. Therefore, LiNO3, CsBr, and RbHCO3 will not form precipitates.
For the following chemical equation: BaBr2(aq)+H2SO4(aq)→BaSO4(s)+2HBr(aq) which will NOT be involved in the net ionic equation?
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.
When carbon dioxide is dissolved in an aqueous solution of sodium hydroxide, the mixture reacts to yield aqueous sodium carbonate and liquid water. Determine the net ionic equation for this process.
CO2(aq)+2OH−(aq)⟶CO2−3(aq)+H2O(l) Begin by identifying formulas for the reactants and products and arranging them properly in chemical equation form: CO2(aq)+NaOH(aq)⟶Na2CO3(aq)+H2O(l)(unbalanced) Balance is achieved easily in this case by changing the coefficient for NaOH to 2, resulting in the molecular equation for this reaction: CO2(aq)+2NaOH(aq)⟶Na2CO3(aq)+H2O(l) The two dissolved ionic compounds, NaOH and Na2CO3, can be represented as dissociated ions to yield the complete ionic equation (note that CO2, a covalent compound, does not dissociate into ions in water): CO2(aq)+2Na+(aq)+2OH−(aq)⟶2Na+(aq)+CO2−3(aq)+H2O(l) Finally, identify the spectator ion(s), in this case Na+(aq), and remove it from each side of the equation to generate the net ionic equation: CO2(aq)+2Na+(aq)+2OH−(aq)⟶2Na+(aq)+CO2−3(aq)+H2O(l) The final net ionic equation is: CO2(aq)+2OH^−(aq)⟶CO3^2−(aq)+H2O(l)
Which of the following dissolves in water to yield hydronium ions?
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.
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.
Identify the missing product in the following acid-base reaction. H2CO3 + 2LiOH -> _____ + 2H2O
Li2CO3 Since one of the reactants is H2CO3, the carbonate ion must be CO2−3. The lithium ion is Li+, therefore, an ionic compound with lithium and the carbonate ion has the formula Li2CO3. Filling this compound in our equation, we can now see that it is balanced. Notice that there are 2OH− ions on the left side (since there are 2LiOH molecules) and 2H+ ions from H2CO3. These combine to form 2HOH or H2O molecules, as indicated. The balanced equation is shown below. H2CO3+2LiOH⟶Li2CO3+2H2O
When ammonium is found in solution, which gas might we anticipate being produced?
NH3 Ammonium salts have the potential to produce ammonia gas. An example reaction is NH4NO3(aq)+KOH(aq)⟶NH3(g)+KNO3(aq)+H2O(l) SO2 is formed as a gas as a result of reactions with sulfites and bisulfites. CO2 is formed as a gas as a result of reactions that produce carbonates and bicarbonates. H2S is formed as a result of reactions that produce sulfides.
Which of the following compounds is water soluble?
Na2CrO4 These anions all typically result in insoluble compounds, except when the cation is a group one metal such as sodium. Therefore, Na2CrO3 is a water soluble compound.
Fill in the blanks with reactants and products in the balanced equation for the acidification reaction of sodium sulfide by hydrobromic acid.
Na2S (aq) + 2HBr (aq) -> 2NaBr (aq) + H2S (g) Hydrogen sulfide, H2S, will be evolved in the reaction. The sulfide ion has a charge of minus two, so the formula of sodium sulfide is Na2S. The formula of hydrobromic acid is HBr. So part of the reaction will be as shown below. Na2S(aq)+HBr(aq)⟶H2S(g)+? The sodium and the bromine in the reactants are missing in the products. They must be added. The complete reaction is shown below. Na2S(aq)+2HBr(aq)⟶H2S(g)+2NaBr(aq)
What is the formula for the precipitate that forms? (Note that there is no way to do subscripts so assume all numbers are subscripts in these choices).
PbI2
If we expect a precipitate to be formed in a certain reaction that takes place in solution, this implies that:
at least one of the products is insoluble If precipitation is expected from a reaction in solution, this must mean that one of the products is insoluble. Precipitates will not form if all products of a reaction are soluble.
What is the type of reaction involved in the following equation? H2SO4(aq)+Zn(s)→H2(g)+ZnSO4(aq)
displacement reaction The reaction involves one component, H2 of the compound, H2SO4 is replaced by Zn metal. Thus, it is a displacement reaction.
Ionic reactions in which ions are exchanged between reactants are called:
double displacement reactions Since an ionic equation will often involve two ionic solids swapping components, where anions dissociate from cations and interact with the other cations in solution, this can be called a double displacement reaction.
Which of the following elements/compounds will likely participate in a chemical reaction?
nitroglycerin Nitroglycerin is very reactive, while helium and neon are noble gases and don't react easily because the valence level is full.
What are the spectator ions in this reaction?
potassium and nitrate
A base is something that:
produces an OH− ion when dissolved in water ' A base is a substance that will dissolve in water to yield hydroxide ions (OH−). An acid is a substance that will dissolve in water to yield hydronium ions (H3O+).
In a chemical equation, the number of atoms of a particular element that are present in a formula unit or molecule of a compound is indicated by a:
subscript Subscripts indicate how many atoms of a particular element are present in a formula unit or molecule of a compound. Coefficients tell us how many molecules of a substance are involved in the reaction and superscripts indicate a charge on an element or substance. A plus sign separates multiple reactants or products in a chemical equation.
If precipitation is not expected from a reaction, which of the following is indicated?
the products are soluble If precipitation is not expected from a reaction, it is an indication that the products are soluble. Precipitates form from insoluble products of a reaction.
