# Tutor profile: Audrey S.

## Questions

### Subject: Organic Chemistry

Why is acetic acid more acidic than phenol?

If you deprotonate both the acetic acid and phenol there is a negative charge on an oxygen in both. When you draw resonance for phenol the negative charge is shared on 1 oxygen and 3 carbons. When you draw resonance for acetic acid the negative charge is shared between 2 oxygens. Since oxygen is more electronegative than carbon, acetic acid is the weaker conjugate base and stronger acid.

### Subject: Basic Math

Fractions: add, subtract, mutiply and divide the following two fractions: $$(a)\frac{3}{5}, (b)\frac{2}{7}$$ For multiplication use $$a\times{b}$$ For division use $$a\div{b}$$ For addition use $$a +{b}$$ For subtraction use $$a-b$$

Multiplication: $$\frac{3}{5} \times \frac{2}{7}$$ To multiply the fractions you will multiply the numerators to calculate the new numerator and also multiply the denominators to calculate the new denominator. Numerator: $${3} \times {2}=6$$ Denominator: $${5} \times {7}=35$$ thus, $$\frac{3}{5} \times \frac{2}{7}=\frac {6}{35}$$ $$\frac{6}{35}$$ cannot be simplified any further so this is the final answer. Division: $$\frac{3}{5} \div \frac{2}{7}$$ To divide you will flip the second then multiple $$\frac{3}{5} \times \frac{7}{2}= \frac{21}{10}$$ $$\frac{21}{10}$$ cannot be simplified any further so this is the final answer. The answer could also be shown as a mixed fraction $$2\frac{1}{10}$$. Addition: $$\frac{3}{5}+ \frac{2}{7}$$ To add fractions they must have like denominators, meaning the denominator must be the same for both fractions. You can find the least common denominator (LCD) by mutiplying the denominators. $$5 \times 7 = 35 $$ this means that the least common denominator is 35 Fraction a: to make the denominator 35 you will multiply it by 7. You have to multiply the whole fraction a by a fraction equivalent to 1. To make the fraction be equivalent to 1 and have a 7 in the denominator the fraction will be $$\frac{7}{7}$$ $$\frac{3}{5} \times \frac{7}{7} = \frac{21}{35}$$ Fraction b: you will follow the same process as fraction a resulting in mutiplying fraction b by $$\frac{5}{5}$$ $$\frac{2}{7} \times \frac{5}{5} = \frac{10}{35}$$ last step you will add the two fractions together, you will do this by adding the numerators but the denominator will stay the same. $$\frac{21}{35} + \frac{10}{35}= \frac{31}{35}$$ $$\frac{31}{35}$$ cannot be simplified any further so this is the final answer. Subtraction: You will do the same steps in addition to find the least common denominator for both fractions. Then instead of adding the fractions you use subtraction. $$\frac{21}{35} - \frac{10}{35}= \frac{11}{35}$$ $$\frac{11}{35}$$ cannot be simplified any further so this is the final answer.

### Subject: Basic Chemistry

_Na (s) +_$$Cl_{2}$$ (g) --> _NaCl (s) (1)Balance the reaction (2)Choose the type of reaction that is occurring: A. Combination reaction B. Decomposition reaction C. Single-replacement reaction D. Double-replacement reaction E. Combustion reaction

(1)ANSWER: $$2Na (s) + Cl_{2} (g) \longrightarrow 2NaCl (s)$$ (1)EXPLANATION: To balance a reaction you must make sure that the number of same elements matches on the left side ( otherwise known as the reactants) and the right side (otherwise known as the products). We are given 1 sodium (Na) and 2 Chlorine (Cl) on the left and 1 Na and 1 Cl on the right, this is not balanced because there is 1 more Cl on the left than there is on the right. To balance the Cl we will put a 2 in front of the product as indicated below $$Na (s) + Cl_{2} (g) \longrightarrow 2NaCl (s)$$ At this point we have 2 Cl and 1 Na on the reactant side and 2 Cl and 2 Na on the product side. The Na is not balanced because there is 1 more Na on the product side. To balance the Na a 2 can be added in front of the Na on the reactant side, shown below. $$2Na (s) + Cl_{2} (g) \longrightarrow 2NaCl (s)$$ There are 2 Na and 2 Cl on the reactant side which matches the 2 Na and 2 Cl on the product side, making the reaction balanced. (2) ANSWER: A.Combination Reaction (2) EXPLANATION: Combination reaction: two compounds combine to created one compound $$A+B \longrightarrow AB$$ Decomposition reaction: one compound decomposes into two compounds $$AB \longrightarrow A+B$$ Single-replacement reaction: one element replaces a similar element in a compound $$A+BC \longrightarrow AC+B$$ Double replacement reaction: the positive and negative ions of two ionic compounds exchange places and thus form two new compounds. $$AB + CD \longrightarrow AD + CB$$ (A and C are positively charged ions; B and D are negatively charged ions) Combustion reaction: a type of combination reaction in which a substance reacts with oxygen, releasing energy, water and carbon dioxide. $$C_{x}H_{y} + O_{2} \longrightarrow H_{2}O + CO_{2}$$ (where x and y are integers) From the definitions above we can discern that this is a combination reaction, since the Sodium and Chlorine are combining to from one compound, NaCl.

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