# Tutor profile: Kaitlyn F.

## Questions

### Subject: Organic Chemistry

What is the IUPAC name for CH3CH2C(CH3)2CH2CH(CH3)2?

First draw out the line structure (omitting the hydrogens): C C-C-C-C-C-C C C First we find the longest chain as our parent chain which is 6 C. So the base of our name is "-hexane." Then we identify the constituents, and there are 3 methyl groups : trimethyl Now we assign which carbon they are attached to. We also want to go with the lowest number as our final answer: ie this can be 3,3,5 trimethylhexane or 2,4,4 trimethylhexane. The correct answer is 2,4,4-trimethylhexane.

### Subject: Geometry

In a 30-60-90 triangle what is the length of the shortest side if the hypotenuse is 6?

Any triangle with a 90 degree angle is a right triangle, and we can use Pythagorean Theorem to solve the problem. The shortest side of the triangle would use opposite side of the 30 degree angle. It would also be the adjacent side to the 60 degree angle. (Then using a pneumonic: soh-cah-toa) sin(30) = X/6 or cos (60)=X/6 To solve for X (make sure the calculator is in degree mode NOT radian mode): 6*sin(30) = 3 or 6*cos(60) = 3 The correct answer is: "3 is the length of the shortest side of a 30-60-90 triangle if the hypotenuse is 6."

### Subject: Chemistry

How many grams of CaCl2 should be dissolved in 750 ml of water to make a 0.25 M solution of CaCl2?

So to start, we need to convert/define things: 0.25 M = 0.25 mol/L 750 mL=0.750 L CaCl2 molar mass= (40.078)+(2*35.453)=110.984g/mol To solve the problem, we can use dimensional analysis to ensure that the units are correct and we end up with what we are looking for. Basically we are going to convert Molarity and volume to moles to grams all at once. Dimensional Analysis gives us: (0.25mol/L)*(0.750 L)*(110.984g/1mol) = 20.8095g Taking SigFigs into consideration (there are 2 sig figs) The correct answer is 21g of CaCl2 is needed to create 750mL of a 0.25M solution.

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