Browning guacamole on a food truck line is the reaction slowed on purpose, with temperature, oxygen and acidity as rate factors, in one SC190 Unit 2 discussion board post. Searches like "sc 190 unit 2 assignment example", "sc190 unit 2 sample" and "sc190 unit 2 example" land here.
What a finished SC190 Unit 2 discussion board post looks like
Three paragraphs of about 300 words and one reply. The first sets the problem: a batch made at ten in the morning is gray-brown at the surface by the afternoon rush. The second names the chemistry, polyphenol oxidase catalyzing the reaction of phenols with oxygen to form quinones that link into brown pigment. Then the levers: plastic wrap pressed onto the surface lowers the oxygen reaching it, a concentration effect. Lime juice pushes the pH below the enzyme's working range. Holding the bowl on ice slows everything, and the post estimates that with an assumed activation energy of 50 kJ/mol, cooling from 22 to 4 degrees Celsius cuts the rate by a factor of about 3.8. The third paragraph ranks the three and argues that excluding oxygen does the most because it removes a reactant.
How a SC190 Unit 2 example is structured
The post follows the prompt's likely order, reaction, factors, choice, but spends most of its words on the factors, because SC190 frames this unit around what controls rate. Each factor gets one sentence naming the principle and one naming the kitchen action: concentration and surface contact, temperature and the Arrhenius relationship, catalyst activity and the enzyme's sensitivity to pH. The temperature estimate is flagged as illustrative, with its assumed activation energy stated so a reader can check the factor of 3.8 or substitute a better value. A short sentence clarifies that the enzyme is a catalyst, speeding the reaction without being consumed, which is why a small amount browns a whole bowl. One cited source covers the enzyme chemistry. The reply beneath, near 110 words, engages a classmate who chose rust on a bicycle chain.
A reaction worth slowing
The post begins with a cost, a batch discarded every afternoon, so the question of rate arrives as a practical problem before any chemistry is named.
Oxygen treated as a reactant
Plastic wrap pressed onto the surface is described as lowering the concentration of one reactant at the reaction site, the same lever the unit's rate laws describe.
Temperature estimated with a stated assumption
An activation energy of 50 kJ/mol is assumed and labeled, and the Arrhenius ratio between 295 K and 277 K gives a slowdown of roughly 3.8 times.
Acid aimed at the catalyst
Lime juice works on the enzyme rather than the reactants, lowering the pH until polyphenol oxidase loses activity, which the post keeps separate from a concentration effect.
A classmate's rusting chain
The reply asks whether winter road salt counts as a rate factor for the classmate's chain, and suggests it does, since dissolved salt makes the water film a better conductor for corrosion.
Where marks go in SC190 Unit 2
In SC190, a post that names a reaction and stops, browning happens, misses the point of a unit built around what controls rate. Factors listed without mechanism come next: keeping it cold earns little until the post says that lower temperature reduces the fraction of collisions with enough energy. Confusing a catalyst with a reactant, such as saying the enzyme gets used up, costs accuracy credit, as does treating pH as a concentration effect on the reactants. Numbers quoted without their assumptions, a slowdown factor with no activation energy stated, invite a comment. A reaction nobody would want slowed answers a different question. Replies are graded on substance, and asking the classmate which factor they could actually change tends to earn more than praise for the choice.
Get a SC190 Unit 2 example written to your instructions
Name the reaction you would like to slow, from a kitchen, a garage, a job or anywhere else, then add the SC190 board wording and grading rubric. Post and reply get written around that reaction, each rate factor tied to a practical action. Free for the first request, it usually lands within 24-48h.
SC190 Unit 2 questions, answered
Does the reaction have to be one I have seen myself?
Most prompts in this unit ask for an everyday reaction, and one you have actually watched gives the post its specific details: how long it took, what you tried and what happened. Food spoilage, rust, fading fabric and battery drain all work. What matters is that at least one rate factor can be changed in practice.
Is it acceptable to estimate the temperature effect with Arrhenius?
Yes, if the assumption is stated. The activation energy for an everyday reaction is rarely known exactly, so the post can assume a reasonable value, label it, and show the ratio it gives. Graders reward the reasoning and the transparency more than the exact factor, and a stated assumption protects the post from a precision comment.
How is a catalyst different from the other rate factors?
Temperature and concentration change how often effective collisions happen along the same pathway. A catalyst provides a different pathway with a lower activation energy and is regenerated afterward, so a small amount keeps working. Inhibiting a catalyst, as acid does to the browning enzyme, removes that faster route rather than slowing the original one.