# Tutor profile: Yikun L.

## Questions

### Subject: Pre-Algebra

Use the following function rule to find f(16). f(x) = x^0.5+8

f(16)=16^0.5+8=12

### Subject: Basic Math

In a sack of 50 marbles, there are 20 more red marbles than blue marbles. All of the marbles in the sack are either red or blue. How many blue marbles are in the sack?

Assume there are x blue marbles, then the number of red marbles is x+20. There are 50 marbles in total, so x+x+20=50. x=15, which means there are 15 blue marbles x+20=35, which means there are 35 red marbles.

### Subject: Basic Chemistry

Ethyl acetate, an undesirable side-product formed during the fermentation step of beer brewing, contains 54.53% C, 9.15% H, and 36.32% O by mass. Its molar mass is 88.1 g/mol. a) What is the empirical formula of ethyl acetate? b) What s the molecular formula of ethyl acetate?

a) Assume the sample of ethyl acetate has a mass of 100g. C H O Mass/g 54.53 9.15 36.32 Molar mass/ g/mol 12.01 1.008 16.00 # of moles 4.540 9.08 2.27 net ratio of moles 2 4 1 C:H:O=2:4:1, so the empirical formula of ethyl acetate is C2H4O. b) The first step is to calculate the molar mass of ethyl acetate. Mr(C2H4O)=12.01*2+1.008*4+16.00*1=44.05g/mol 88.01/44.05=2 so the molecular formula is C4H8O2.

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