Chemistry 101 Week 9
Identify the balanced chemical equation. Select the correct answer below: 2 Fe2O3+3 C→4 Fe+3 CO2 H2O2→H2O+O2 SO2+O2+H2O→4 H2SO4 2 Mg+HCl→MgCl2+H2
Correct answer: 2 Fe2O3+3 C→4 Fe+3 CO2 The balanced equation will have equal number of atoms of each element on both sides of the equation. The balanced equation has 4 Fe,3 C, and 6 O atoms on each side.
What mass of Cl2 is required to produce 21.4 g HCl? H2+Cl2⟶2HCl Select the correct answer below: 16.5 g 20.8 g 26.7 g 83.2 g
Correct answer: 20.8 g The coefficients in the balanced chemical equation can be used as the stoichiometric factor between HCl and Cl2. Molar mass converts between grams and moles. 21.4 g HCl(1 mol HCl36.461 g HCl)(1 mol Cl22 mol HCl)(70.906 g Cl21 mol Cl2)=20.8 g Cl2
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. The coefficient 2 is a coefficient of the product, not of the reactants.
From the following balanced equation, 2H2(g)+O2(g)⟶2H2O(g) how many grams of H2O can be formed from 5.58g H2? Select the correct answer below: 49.9g 0.624g 99.8g 5.54g
Correct answer: 49.9g The coefficients in the balanced chemical equation can be used as the stoichiometric factor between H2O and H2. Molar mass converts between grams and moles. 5.58gH2×1molH22.016gH2×2molH2O2molH2×18.015gH2O1molH2O=49.9gH2O
If 45.0 g CH3OH react, how many grams of water can we expect to be produced according to the following equation: 2CH3OH+3O2→2CO2+4H2O Select the correct answer below: 9.64 19.3 38.6 50.6
Correct answer: 50.6 First, calculate the number of moles of CH3OH that are produced, then use a ratio to solve for the number of H2O moles that should be formed. Finally, convert the moles of H2O to grams of H2O. 45.0 g CH3OH(1 mole CH3OH32.042 g CH3OH)(4 moles H2O2 moles CH3OH)(18.015 g H2O1 mole H2O)=50.6 g H2O
If two compounds in a chemical reaction are listed with the coefficients 2 and 5 respectively, which is NOT a possible numerical combination of these compounds that will result in their complete reaction? Select the correct answer below: 4 and 10 100 and 250 8 and 18 40 and 100
Correct answer: 8 and 18 Any numerical combination of these compounds that results in a complete reaction will reduce to a 2:5 ratio. 8 and 18 is the only option that does not obey the explicit 2:5 ratio dictated by the coefficients in the chemical equation. All of the other values reduce to a 2:5 ratio.
If 5.50 g NO react completely, how many grams of NO2 can we expect to be produced according to the following equation: 2NO+O2→2NO2 Select the correct answer below: 4.21 8.43 16.8 5.50
Correct answer: 8.43 The coefficients in the balanced chemical equation can be used as the stoichiometric factor between NO and NO2. Molar mass converts between grams and moles. 5.50 g NO(1 mole NO30.006 g NO)(2 moles NO22 moles NO)(46.005 g NO21 mole NO2)=8.43 g NO2 Your answer:
How many grams of sodium chlorate are required to generate 50.0 g sodium chloride according to the following equation: 2NaClO3→2NaCl+3O2 Select the correct answer below: 91.1 g 102 g 45.5 g 16.3 g
Correct answer: 91.1 g The coefficients in the balanced chemical equation can be used as the stoichiometric factor between NaCl and NaClO3. Molar mass converts between grams and moles. 50.0 g NaCl(1 mole NaCl58.443 g NaCl)(2 moles NaClO32 molesNaCl)(106.44 g NaClO31 mol NaClO3)=91.1 g NaClO3
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 According to the solubility rules hydroxides of group one metals as well as barium are soluble, but hydroxides of transition metals are insoluble.
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 double replacement reaction are NaNO3 and AgOH. Because hydroxides are insoluble the reaction will produce precipitation.
Which of the following compounds is water insoluble? Select the correct answer below: Na2SO4 MgSO4 K2SO4 PbSO4
Correct answer: PbSO4 Sulfates (SO4) are typically soluble, but lead sulfate (PbSO4) is an exception to this rule, so lead sulfate will form a precipitate and therefore is insoluble.
Balance the following equation: X2+Y2⟶XY3 Select the correct answer below: X2+Y2⟶XY3 2X2+Y2⟶3XY3 X2+3Y2⟶2XY3 X2+Y2⟶2XY3
Correct answer: X2+3Y2⟶2XY3 First, write the unbalanced equation: X2+Y2⟶XY3 . To balance X , add a coefficient of 2 in front of XY3. X2+Y2⟶2XY3 To balance Y , add a coefficient of 3 in front of Y2. X2+3Y2⟶2XY3 The equation is balanced.
To convert from the mass of one substance to the mass of another substance in a chemical equation, we will need to use: Select the correct answer below: the molar mass of the first substance the molar mass of the second substance the stoichiometric factor involving the two substances all of the above
Correct answer: all of the above We will need to use three separate conversion factors to convert from the mass of one substance to the mass of another. We need to first convert to moles, then to moles of the other substance, and then back to grams of the other substance.
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.
If we expect a precipitate to be formed in a certain reaction that takes place in solution, this implies that: Select the correct answer below: the products are soluble at least one of the products is insoluble precipitation is not related to the solubility of a reaction there is not enough information to answer this question
Correct answer: 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.
Which type of anion will typically result in an insoluble compound? Select the correct answer below: chromate bicarbonate chlorate acetate
Correct answer: chromate According to solubility rules chromates will be insoluble except when combined with group one metal cations or the ammonium ion.
The relative numbers of reactants and products are represented by: Select the correct answer below: products reactants coefficients subscripts
Correct answer: coefficients Coefficients, which are numbers placed to the left of each compound in the equation, indicate the relative numbers of reactants and products that react.
What is the type of reaction involved in the following equation? C2H4(g)+H2(g)→C2H6(g) Select the correct answer below: displacement reaction double displacement reaction decomposition reaction combination reaction
Correct answer: combination reaction This reaction is the synthesis reaction, involving hydrogenation of ethene to form ethane. It is an example of a combination reaction.
Identify the reaction where a single compound separates into multiple compounds or elements. Select the correct answer below: displacement reaction decomposition reaction double displacement reaction combination reaction
Correct answer: decomposition reaction Decomposition reactions are those in which a single compound separates into multiple compounds or elements. The general form is: AB→A+B where A and B represent chemical species or parts of chemical species.
Sodium azide, NaN3(s), is responsible for the rapid deployment of airbags during a car crash. The reaction is initiated by an electrical discharge and produces nitrogen gas and elemental sodium. This is an example of which type of reaction? Select the correct answer below: displacement reaction combination reaction double displacement reaction decomposition reaction
Correct answer: decomposition reaction From the statement, there is one reactant, sodium azide, and the products are nitrogen gas and elemental sodium. The full chemical equation is 2NaN3(s)→2Na(s)+3N2(g) This is an example of a decomposition reaction, because the one reactant, sodium azide (NaN3), is separated into two products, Na and N2.
Calcium carbonate breaks down into calcium oxide and liberates carbon dioxide. The whole reaction is driven by heat. What type of reaction is this? Select the correct answer below: combination reaction displacement reaction decomposition reaction double displacement reaction
Correct answer: decomposition reaction The reaction involves breaking a single compound (reactant) into multiple compounds (products). Thus, it is decomposition reaction. This reaction can be written as: CaCO3→CaO+CO2
Classify the following reaction as combination, decomposition, displacement, or double displacement reaction: BaCl2 (aq)+K2CrO4 (aq)→BaCrO4 (s)+2KCl (aq) Select the correct answer below: combination decomposition displacement double displacement
Correct answer: double displacement The reaction involves the exchange of positive ions between two ionic compounds in an aqueous solution. Barium exchanges with potassium. One product, BaCrO4, precipitates from solution.
Acid-base gas evolution reactions come under which type of reactions? Select the correct answer below: displacement reaction double displacement reaction decomposition reaction combination reaction
Correct answer: double displacement reaction Acid-base gas evolution reactions involve a double displacement reaction that forms water and an unstable molecule that then decomposes into a gas and a stable compound.
Substances on the same side of a chemical equation are separated by a: Select the correct answer below: coefficient forward arrow plus sign subscript
Correct answer: 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.
The substances undergoing a chemical reaction are known as: Select the correct answer below: products reactants coefficients none of the above
Correct answer: reactants The substances undergoing a chemical reaction are known as reactants. The substances produced in a reaction are products. Coefficients tell us how many molecules of a substance are involved in the reaction.
According to the following reaction, if 69g of KClO3 decomposes, how many grams of oxygen will form: 2KClO3→2KCl+3O2 Your answer should have two significant figures.
Correct answers:27 g First, calculate the number of moles of KClO3 that decomposed: 69gKClO3×1molKClO3122.548gKClO3≈0.563045molKClO3 Next, use the ratio of O2 to KClO3 to find the number of moles of O2 formed. 0.563045molKClO3×3molO22molKClO3≈0.844567molO2 Finally, convert the moles of O2 to grams of O2: 0.844567molO2×31.998gO21molO2≈27.0245gO2 The answer should have two significant figures, so round to 27gO2.
The combination of iron and oxygen produces rust. Complete the combination reaction for this process below by determining the molecular formula for the iron (III) oxide that is formed. Do not include the state of the product. Provide your answer below:4Fe+3O2-->2
Correct answers:4Fe+3O2→2Fe2O3 To determine the molecular formula for the product, we must look at the charges for each element in the substance. It is given that the oxidation state for iron is +3 and the oxidation state for oxygen is always −2. Therefore, the molecular formula for iron (III) oxide is Fe2O3. The equation must be balanced. There are four iron atoms on the left side, and the coefficient of the rust molecule is two, so there must be two iron atoms per rust molecule. Likewise, there are six oxygen atoms on the left side, which means each rust molecule must account for three. Therefore, the completed reaction can be written as shown below. 4Fe+3O2⟶2Fe2O3
Fill in the blank coefficient to balance the following chemical equation. Your answer should be a whole number. Provide your answer below: CH4+H2O-->CO+ H2
First, write the unbalanced equation. CH4+H2O⟶CO+H2 The coefficients of CH4 and CO are given as 1 (not written). They must be the same because each has 1 carbon atom. The coefficient in front of H2O must also be 1 to balance the oxygen atoms with CO. To balance H, notice that there are 6 hydrogen atoms on the left side of the equation, and each molecule of H2 has 2 hydrogen atoms. To get 6 hydrogen atoms on the right side, set the coefficient of H2 to 3. CH4+H2O⟶CO+3H2
Fill in the blank coefficients to balance the following chemical equation. Your answers should be whole numbers. Provide your answer below: H2O2+SO2-->H2SO4
First, write the unbalanced equation. H2O2+SO2⟶H2SO4 The equation is balanced with 1 as the coefficient for all reactants and products. 1H2O2+1SO2⟶1H2SO4 Element Reactants Products Balanced?H(1×2)=2(1×2)=22=2, yesO(1×2)+(1×2)=41×4=44=4, yes S1×1=11×1=11=1, yes
Fill in the blank coefficients to balance the following chemical equation. Your answers should be whole numbers.SiCl4+ Mg--> MgCl2+Si
First, write the unbalanced equation: SiCl4+Mg⟶MgCl2+Si to balance Cl, add a coefficient of 2 in front of MgCl2. SiCl4+Mg⟶2MgCl2+Si To balance Mg , add a coefficient of 2 in front of Mg. SiCl4+2Mg⟶2MgCl2+Si The equation is now balanced. The coefficient in front of both Mg and MgCl2 is 2.
