Reaction Types
Mole Calculations, Empirical, & Molecular Formula
Miscellaneous
Solutions
Labs
100
What type of reaction occurred?
BaCl2(aq) + MgSO4(aq) → BaSO4(s) + MgCl2(aq)
double displacement/replacement
100
January 2013, #61
The equation below represents the reaction between 1-butene and bromine to form the compound 1,2-dibromobutane, C4H8Br2. Write the empirical formula for the product.
1,2-dibromobutane = C4H8Br2
empirical formula = C2H4Br
100
January 2013, #63
Ammonium chloride is dissolved in water to form a 0.10 M NH4Cl(aq) solution. This dissolving process is represented by the equation below.
NH4Cl(s) + heat → NH4+(aq) + Cl-(aq)
State evidence that indicates the dissolving of ammonium chloride is an endothermic process.
Heat is absorbed in the rxn.
Heat is a reactant.
Heat is on the left.
100
June 2012, #59
A total of 1.4 moles of sodium nitrate is dissolved in enough water to make 2.0 liters of an aqueous solution. The gram-formula mass of sodium nitrate is 85 grams per mole.
Determine the molarity of the solution.
molarity = moles solute / liters solvent (Table T)
= 1.4 mol NaNO3 / 2 L H2O
= 0.7M
100
What is the difference between an endothermic and exothermic reaction?
endothermic = rxn absorbs heat
exothermic = rxn releases (emits) heat
200
June 2012, #52
The reaction between aluminum and an aqueous solution of copper(II) sulfate is represented by the unbalanced equation below.
Al(s) + CuSO4(aq) → Al2(SO4)3(aq) + Cu(s)
Identify the type of chemical reaction represented by the equation.
single replacement
200
June 2012, #57
A total of 1.4 moles of sodium nitrate is dissolved in enough water to make 2.0 liters of an aqueous solution. The gram-formula mass of sodium nitrate is 85 grams per mole.
Show a numerical setup for calculating the mass of the solute used to make the solution.
molar mass NaNO3 = 23g + 14g + (16 x 3)g = 85g
1 mol/85g = 1.4 mol/x
x = 85g x 1.4
(x = 119g)
200
January 2013, #60
The equation below represents the reaction between 1-butene and bromine to form the compound 1,2-dibromobutane, C4H8Br2. Determine the gram-formula mass of 1-butene.
1-butene = C4H8
molar mass = (12g x 4) + (1g x 8) = 48g + 8g
= 56g
200
June 2012, #56
A total of 1.4 moles of sodium nitrate is dissolved in enough water to make 2.0 liters of an aqueous solution. The gram-formula mass of sodium nitrate is 85 grams per mole.
Write the chemical formula for the solute in the solution.
nitrate = NO3- (Table E)
sodium = Na+ (Group 1)
= NaNO3
200
In the Nail Lab, how did we determine which product was the precipitate (copper or iron sulfate)?
Copper was the solid product, while iron sulfate is liquid (because iron sulfate is soluble in water). A precipitate is a solid product.
300
What type of reaction occurred?
2KOH(aq) + H2SO4(aq) → K2SO4(aq) + 2H2O(l)
acid-base
AH + BOH → AB (salt) + H2O
300
January 2012, #78
Vitamin C, also known as ascorbic acid, is water soluble and cannot be produced by the human body. Each day, a person’s diet should include a source of vitamin C, such as orange juice. Ascorbic acid has a molecular formula of C6H8O6 and a gram-formula mass of 176 grams per mole.
What is the empirical formula of ascorbic acid?
C3H4O3
300
June 2012, #53
The reaction between aluminum and an aqueous solution of copper(II) sulfate is represented by the unbalanced equation below.
Al(s) + CuSO4(aq) → Al2(SO4)3(aq) + Cu(s)
Balance the equation in your answer booklet, using the smallest whole-number coefficients.
2Al(s) + 3CuSO4(aq) → Al2(SO4)3(aq) + 3Cu(s)
300
June 2012, #58
A total of 1.4 moles of sodium nitrate is dissolved in enough water to make 2.0 liters of an aqueous solution. The gram-formula mass of sodium nitrate is 85 grams per mole.
Compare the boiling point of the solution at standard pressure to the boiling point of H2O at standard pressure.
The solution of sodium nitrate and water has a higher BP than plain H2O.
300
How many molecules of methane, CH4, are in 0.75 moles of methane?
= 0.75 mol * (6.02 x 1023)
= 4.52 x 1023 molecules of methane
400
What type of reaction occurred?
C5H12 + 8O2 → 5CO2 + 6H2O
combustion
CxHy + O2 → CO2 + H2O
400
January 2012, #76
Vitamin C, also known as ascorbic acid, is water soluble and cannot be produced by the human body. Each day, a person’s diet should include a source of vitamin C, such as orange juice. Ascorbic acid has a molecular formula of C6H8O6 and a gram-formula mass of 176 grams per mole.
Determine the number of moles of vitamin C in an orange that contains 0.071 gram of vitamin C.
1 mol/176g = x mol/0.071g
x = 0.0004 moles
400
June 2012, #68
Today, it is known that the chemical formula for potassium aluminum sulfate is KAl(SO4)2•12H2O. It is a hydrated compound because water molecules are included within its crystal structure. There are 12 moles of H2O for every 1 mole of KAl(SO4)2. The compound contains two different positive ions. The gram-formula mass of KAl(SO4)2•12H2O is 474 grams per mole.
Show a numerical setup for calculating the percent composition by mass of water in KAl(SO4)2•12H2O.
The 12 water molecules weigh 12 x 18g = 216g
% by mass = (mass part / mass whole) * 100%
Water is the part. KAl(SO4)2•12H2O is the whole.
% by mass = (216g/474g) * 100%
= (45.6%)
400
January 2013, #62
Ammonium chloride is dissolved in water to form a 0.10 M NH4Cl(aq) solution. This dissolving process is represented by the equation below.
NH4Cl(s) + heat → NH4+(aq) + Cl-(aq)
Determine the number of moles of NH4Cl(s) used to produce 2.0 liters of this solution.
0.10M NH4Cl means that there are 0.10 moles of NH4Cl in 1 L of solution.
So, in 2.0 L of solution, there are:
0.10 * 2 = 0.20 moles NH4Cl
400
List all reactants and all products in the following chemical reaction:
reactants: 2H2, O2
products: 2H2O
500
Carbonates will break down upon the addition of heat, as represented by the following reaction
CaCO3(s) + heat → CaO(s) + CO2(g)
What type of reaction occurred?
decomposition
AB → A + B
500
June 2012, #55
The reaction between aluminum and an aqueous solution of copper(II) sulfate is represented by the unbalanced equation below.
Al(s) + CuSO4(aq) → Al2(SO4)3(aq) + Cu(s)
Determine the total mass of Cu produced when 1.08 grams of Al reacts completely with 9.58 grams of CuSO4 to produce 6.85 grams of Al2(SO4)3
2Al(s) + 3CuSO4(aq) → Al2(SO4)3(aq) + 3Cu(s)
1.08 g Al = 0.04 mol
9.58 g CuSO4 = 0.06 mol
6.85 g Al2(SO4)3 = 0.02 mol
2 mol Al = 3 mol Cu so...
0.04 mol Al = 0.06 mol Cu
0.06 mol Cu x 63.546 g/mol = 3.81g Cu
500
January 2013, #68
Nitrogen gas and oxygen gas make up about 99% of Earth’s atmosphere. Other atmospheric gases include argon, carbon dioxide, methane, ozone, hydrogen, etc. The amount of carbon dioxide in the atmosphere can vary. Data for the concentration of CO2(g) from 1960 to 2000 are shown in the table below.
Show a numerical setup for calculating the mass of carbon dioxide in a 100.0-gram sample of air taken in 1980.
The table says ppm, so use that formula.
ppm = (mass solute / mass solution) * 1,000,000
338.7 = (mass solute / 100g) * 1,000,000
Rearrange the equation.
mass solute = (338.7 / 1,000,000) * 100
500
January 2013, #65
Ammonium chloride is dissolved in water to form a 0.10 M NH4Cl(aq) solution. This dissolving process is represented by the equation below.
NH4Cl(s) + heat → NH4+(aq) + Cl-(aq)
Determine the minimum mass of NH4Cl(s) required to produce a saturated solution in 100. grams of water at 40.°C.
Table G!
At 40oC, you can dissolve ~47g NH4Cl.
500
Write the molecular formula for aluminum chromate.
chromate = CrO42- (Table E)
aluminum oxidation state = 3+ (Periodic Table)
To balance the charge, you need 3 chromates (6-) and 2 aluminums (6+)
Al2(CrO4)3