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skylarschumacher7
09.01.2021 •
Chemistry
Caffeine has the molecular formula, C8H10N4O2. What is the percent composition of caffeine?
Select one:
a) 33.33% C, 41.67% H, 16.67% N, and 8.33% O
b) 49.48% C, 5.19% H, 28.85% N, and 16.48% O
c) 25% C, 25% H, 25% N, 25% N, and 25% O
d) 27.92% C, 2.34% H, 32.56% N, and 37.19% O
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Ответ:
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...56gN32gO
100gabcd
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
Ответ:
"Tidal currents can be defined as the periodic movement of water driven principally, though not necessarily exclusively, by a head difference created by out-of-phase ocean tides at each end of a restriction"From Google.
Explanation: