Concentration
What are the scientific units for concentration (hint: how do we differentiate from density?)
g/100cm3
When balancing equations, do we change the coefficient or the subscript?
coefficient
When a reaction feels cold, that is an indicator it was either an endothermic or exothermic reaction. Which one?
Endothermic
What do we call a chemical reaction that has an equal number of forward reactions as there are reverse reactions?
equilibrium
52 students went and measured the circumfrence of all of the oak trees on campus. The students then went online and referenced the precipation that occurred over the past year. They compared this data to the data that was collected last year.
What is the independent and dependent variable?
IV- precipitation of the various years
DV-circumfrence of tree
In salt water, is the salt the solute or the solvent?
Solute
Can we ever make a single molecule of water? If no, what is the smallest amount of water molecules we can make from a singular reaction?
No. 2
Energy will always flow in one direction. What is that direction energy flows in?
Hight to Low
What does it mean when we say the chemical reaction shifts left?
More Reactants are being made than products
Why is swimming in the ocean easier than swimming in a great lake?
difference in density.
ocean is more dense so we float making swimming easier
Will 40 grams of potassium nitrate dissolve fully in 20 degree celsius water? why or why not?
no.
Above the solubility line
Balance the following equation:
CH4 + Cl2 --> CCl4 + HCl
1 4 1 4
What kind of reaction (endothermic or exothermic) is being described?
The Reactants have less energy than the products
Endothermic
How will the chemical reaction shift when we take away products?
Shift right
Does spontaneous reacrtions require activation energy? Provide an example to support your answer
No.
Hot hands
How many grams of the solute can disolve in 350 ml of water?
70g
Balance the following equation:
P4O10 + H2O --> H3PO4
1 6 4
In an exothermic reaction, the reactants have _________ energy than the products.
more
How do you know if an equation is reversible?
Is it possible to achieve equilibrium if a reaction is not reversible?
-Yield symbol goes in both directions
-No
The law of conservation of mass is applied under what circumstances?
Closed system
Explain the process of how rock candy is formed.
You must include the vocab: super saturation, concentration, solute and solvent.
Increased temperature usually increases the solubility of solids in liquids. As you increase temperature the average velocity for the particles increases. This allows them to move from one position to another more easily. The change in solubility with change in temperature can be used to create solutions with more solute dissolved than is predicted by the solubility of the substance[1].
Rock candy is produced from a supersaturated solution of sugar. A supersaturated solution is one that holds more than the maximum amount of solute at a given temperature. You can make it by adding more sugar to water than will dissolve at room temperature, heating the mixture until the solubility limit has been increased enough to allow all of the sugar to dissolve, suspending a string in the hot solution, and allowing the solution to cool slowly back to room temperature. The solution remains supersaturated for a long while. Sugar molecules, which are relatively large, are slow to find the proper positions for crystal formation. Meanwhile, collisions with water molecules keep knocking them apart. Eventually, however, solid begins to form on the protected, irregular surfaces of the suspended string. Dissolved sugar molecules collide with the solid precipitating onto the string and gradually create the large, well-formed sugar crystals that we call rock candy[2].
[1]Modified from James Coller ,Nickolas Starkey, MST Chemistry.
[2] Modified from James Coller ,Nickolas Starkey, MST Chemistry.
HBr+Mg(OH)2 --> MgBr2 + H2O
2 1 1 2
Label what each letter is representing.
Picture on board to follow...
A- Potential energy of reactants
B-Activation energy
C-Potential energy of the activated complex
D- Potential energy of products
If you decrease the temperature of the reactants in a reversible chemical reaction, than how will the reaction shift?
Why?
Left.
Less reactants turing into products (less "speed"=less collisions) compared with products turning back into reactants.
If reactants had a potential energy of 20J and then we heated the reactants with 100J of energy and started the reaction. The reaction absorbed 70J of energy compared to the reactants.
1. Was this endo or exothermic?
2. What was the activation energy?
3. What was the potential energy of the activated complex of the reverse reaction?
1. Endothermic
2. 100J
3. 120J