Calculations
Reaction Rates
Conceptual
Previous Units(Acids Bases and Solutions)
Previous Units (Stoich)
100
What is the change in enthalpy (∆ H) for the reaction below. Round to the nearest 0.1 and include proper units.
A + BC -> AB + C
Use the following information.
A + B -> AB ∆ H = -49.0 kJ
BC -> B + C ∆ H = 87.1 kJ
∆ H = 38.1 kJ
100
I have two cups of water. Cup A is 60oC and cup B is 20oC. Which one has more kinetic energy?
Cup A, higher temperature (temperature measures kinetic energy)
100
BONUS REVIEW QUESTION: Lemon juice has a pH of 2. Is lemon juice acidic, basic, or neutral?
Acidic (anything below 7 is an acid, above 7 is a base)
100
Solution A has a pH of 2 and solution B has a pH of 5. How many times more acidic is solution A compared to solution B?
1000 times
100
You have 3 moles of H2 and 2 moles of O2. What is the limiting reactant and what is the excess?
2H2 + O2 -> 2 H2O
H2 is the limiting reactant (Can only make 3 moles of H2O)
O2 is the excess reactant (Could make 4 moles of H2O)
200
You burn a 1.6 g jellybean to warm 12 g of water. The temperature of the water increases 9°C. How many calories of heat did the water absorb? Round 1 digit past the decimal and include the correct ABBREIVIATED unit.
108.0 cal
200
1. How do enzymes/catalyst speed up reactions?
2. How do inhibitors slow down reactions?
1. LOWERING activation energy
2. RAISING activation energy
200
Is this reaction endothermic or exothermic? How can you tell?
Endothermic. Products(end of the graph) have MORE energy than reactants(beginning of the graph) so that means energy was absorbed.
200
Draw two diagrams showing what the particles would look like in a strong acid versus a weak acid. (Draw two pictures)
Strong acid: all or most the particles are separate (dissociate completely)
Weak acid: most of the particles are still together (dissociate partially)
200
What is the percent by mass of Hydrogen in H2O? Round to nearest 0.1% and include percent sign and element symbol.
11.2 % H
300
Calculate the temperature change for a 54 g iron block that absorbed 388 j of heat energy. The specific heat of iron is 0.449 j/goC. Round one digit after decimal and include the abbreviated unit.
16.0 oC (just type C on eClass)
300
What are the three things that must happen in order for a reaction to occur according to collision theory?
1. particles must collide
2. particles must collide with proper orientation
3. there must be enough energy to overcome activation energy barrier
300
You dissolve a substance in a beaker A and the beaker becomes WARM. You dissolve a different substance in beaker B and it becomes COLD. Which beaker contains the exothermic reaction and which one contains endothermic reaction?
Beaker A is exothermic because it is releasing heat, making it feel warm.
Beaker B is endothermic because it is absorbing heat from its surroundings.
300
How many moles of solute are in 200 mL of a 3.4 M solution? Round to nearest 0.01 and include a UNIT.
0.68 mol
300
What is the mass of iron required to make 22.02 grams of iron oxide (Fe2O3)? Round to 0.01 and include unit and substance.
4Fe + 3O2 -> 2 Fe2O3
15.40 g Fe
400
Students burn a mini snickers bar with a can of water above it. The initial temperature of the water is 17.4oC and the final temperature of the water is 91.5oC. The mass of the water in the can is 89.2 g. How many Calories was this snickers bar? Round 2 decimal places and include the correct abbreviated unit.
4.184 j = 1 cal
1 Cal = 1000 cal
Specific heat of water is 4.184 j/g
6.61 Cal
400
Name 4 ways to INCREASE reaction rate
Increase temp
Increase concentration (or number of particles)
Add catalyst/enzyme
Increase surface area (by crushing or breaking up into smaller pieces)
400
Iron has a specific heat of 0.449 j/goC. Water has a specific heat of 4.184 j/goC. Which one requires LESS energy to raise its temperature?
Iron because it has a lower specific heat.
400
You dissolve 110 g of KNO3 in 100 g of water at 20oC. EXPLAIN in steps how you would determine if the solution is saturated, unsaturated, or supersaturated?
1. Find the KNO3 line.
2. Graph the data given (ignore the 100g of water, it's just context)
3. If you end up on the line exactly, it's saturated, Below the line = unsaturated, above the line = supersaturated
4. 110 g of KNO3 in 100 g of water at 20oC is SUPERSATURATED (above the KNO3 line)
400
Convert 3.03 x 1023 molecules of hydrogen gas (H2) to grams. Round to the nearest 0.01 and include abbreviated unit.
1.02 g