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antoniya [11.8K]
3 years ago
11

Caffeine has the molecular formula, C8H10N4O2. What is the percent composition of caffeine?

Chemistry
1 answer:
Debora [2.8K]3 years ago
3 0

Answer:

b) 49.48% C, 5.19% H, 28.85% N, and 16.48% O

Explanation:

we find the mass for each element in one mole by multiplying the number of atoms in one molecule with the atomic mass

mC=8Ac=8*12=96g

mH=10AH=10*1=10g

mN=4AN=4*14=56g

mO=2AO=2*16=32g

by adding the masses together we find the molar mass of the molecule

M=mC+nH+mN+mO=96+10+56+32=194g/mole

we apply the rule of threes to find the percentage of each element

194g..96gC..10gH...56gN....32gO

100g....a...........b...........c.............d

a=(100*96)/194=49.48%C

b=(100*10)/194=5.19%H

c=(100*56)/194=28.85%N

d=(100*32)/194=16.48%O

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Answer:

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As you require 26.0mL of the base to consume all HA, if you add 13mL, the moles of HA will be the half of the initial moles and, the other half, will be A⁻

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<h3>2.75 = pKa</h3>

Knowing pKa = -log Ka

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