## The Limiting Reactant

The limiting reactant or can be called as limiting reagent is the reactant inside the chemical reaction. The limiting reactant tells the amount of product that can be makeup. We use the limiting reaction in order to find a possible solution to calculate the theoretical yield of the chemical reaction. In a chemical reaction, there is a limiting reactant because compound and elements react the way it is based on the mole ratio that is between them when we did the balanced chemical equation. What’s being called an excess reactant is the remaining leftover when the limiting reactant is complete.

To understand more about the limiting reactant topic, our chemistry teacher prepared us a lap called ” The SMORE Lab”. We used chocolate, marshmallows, and crackers to make s’more. We start off with
1. Writing the balanced equation for the making of s’more.
2. Define the type of reaction.
3. Record the total piece of the reactant.
4. The maximum production of s’more and give a reason why.
4. Figure out which is limiting and excess reactant.
5. Figure out the mass of each reactant on the scale.
6. Record the theoretical yield (mass) of s’more.
7. Make the s’mores
8. Write down the actual mass of one s’mores

We know which reactant was limiting because when we make three complete s’more, the pieces (cracker and chocolate) run out first. We then figure out the excess reactant because when we run out of chocolate and crackers, there are marshmallows left.

## Chemistry: Density Lap

In Unit 1, we did a lab experiment about coins density. Density is a characteristic property of a substance. The density of a substance is the relationship between the volume of the substance (how much space it takes up) and the mass of the substance. We can calculate density by taking the mass of the substance and divide it by the volume of the substance (D = m/v). This explains that the objects with different mass but the same volume have different densities.

This lap provides an introduction to the concept of density measurements. Our goal for the density lap was determined the method of finding the density of the coin by using measured volumes and masses to calculate densities then evaluate the result by using error analysis. My chemistry teacher, Ellie, gave me five twenty cents Singaporean coin and let me figure out what is the type of metal the coin made out of. My hypothesis was I think that the metal of twenty Singaporean coins is made out of nickel because the coin was sinking went it is in the water. I then created my own procedure of finding the density of the coin and figure out what type of metal does it made out of.

Here is my procedure:

• Have all of these materials ready: 5 twenty cents coin, a medium graduated cylinder, paper towels, scale, and the dripper.

• Weigh the mass of the five coins
• Take a medium graduated cylinder and add the sink water to (… ml) it’s helpful to have a dripper in case you wanted an accurate volume of water
• Let the cylinder sat still for a few seconds
• Drop the coins into the graduated cylinder slowly and let it sat still for a few seconds
• Measure the new volumes
• Take the initial volumes of the water and subtract the new volume of water
• Plug in all the value needed for the density equation  (plug in the weight of the five coins into mass, next take the difference of the volume and plug it into volume and you’ll get density)
• Make sure to be careful with the accuracy of the water volumes and the sig fig division.

Mass

───── = Density

Volume

• Repeat the same following steps and try out with different water volumes

In conclusion, my hypothesis was supported because the real metal that the coins was made out of is nickel plated steel. In addition to the trails, some unavoidable errors in this lap are that the measurement of the water volumes in the graduated cylinder is never accurate and reading the scale correctly. Moreover, some types of avoidable errors that can be avoided during the lap are: add higher volume in the graduated cylinder so the volume of water stays precise when dropping the coins in, repetition; make sure to dry out the coins before doing another trial otherwise the changes of the volume would not be precise.