# Tutor profile: Uchenna O.

## Questions

### Subject: Organic Chemistry

How many diastereomers are present in 3-methyl-4-chlorohex-1-ene?

The first step here would be to find the number of chiral carbons in this compound. 3-methyl-4-chlorohex-1-ene has two chiral carbons at carbons 3 and 4 specifically. Next to find the number of diastereomers you have to use this formula: # of diastereomers = 2^n (where n is the number of chiral carbons) Since we have 2 chiral carbons, that means we have a total of 2^2 = 4 different diastereomers.

### Subject: Chemistry

Find the mol of the excess reactant left over after 0.50mol hydrogen gas reacts with 0.50mol oxygen gas to give water.

First we must start with a chemical equation using the formulas for the elements and compunds mentioned in the question: H2 + O2 --> H2O But notice that the amount of atoms of each element doesn't match (oxygen specifically), meaning our equation is unbalanced. To balance the oxygen we have to put a 2 in front of the H2O to give 2 oxygen atoms on both sides of the equation. H2 + O2 --> 2 H2O Now if we reevaluate the atoms on both sides, we see that while oxygen is now balanced, our change made the amount of hydrogens unbalanced (2 on left, 4 on right). Now we must add a 2 in front of H2 to balance hydrogen. 2 H2 + O2 --> 2 H2O All atoms now look balanced so we can proceed to the next part. If 2 reactants combine, it's very rare that exact amount react and completely use up each other. One will usually finish before the other because it's limiting thus leaving an excess of the other reactant. In this case we have to use our stoichiometric coefficient in our equation to see how much of the other reactant is needed. We multiply the mol of a reactant by the mol ratio obtained from the equation: 0.50mol H2 * (1mol O2)/(2mol H2) = 0.25 mol O2 AND 0.50 mol O2 * (2mol H2)/(1mol O2) = 1 mol H2 0.50 mol O2 requires 1mol H2 to react completely. However, we only have 0.50mol H2 and thus it is limiting. We also see that we only need 0.25mol O2 to react with 0.5mol H2. We have 0.5mol O2 and thus it's in excess. To find the excess amount, we subtract the required amount from the initial amount: Excess O2 = (0.50 - 0.25) mol O2 = 0.25mol O2

### Subject: Algebra

Find three consecutive numbers that sum up to -15.

Consecutive numbers are integers that come right after another. If we are to represent consecutive numbers algebraically, we can write them as: x, x+1, x+2, x+3..................x+n Since we are dealing with 5 consecutive numbers that sum up to -15 we can make the following expression: x + (x+1) + (x+2) + (x+3) + (x+4) = -15 If we simplify this expression, we get the following: 5x + 10 = -15 Next we want to get all the terms with x alone on one side so we subtract 10 from both sides: 5x = -25 Finally we divide both sides of the equation by 5 thus x = -5 With x = -5, we now know that our 5 consecutive numbers will be -5, -4, -3, -2, and -1.

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