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4 years ago

What is the percent composition of carbon in caffeine (C₈H₁₀N₄O₂)?

1 answer:

5 0

Caffeine has the following percent composition: carbon 49.48%, hydrogen 5.19%, oxygen 16.48% and nitrogen 28.85%. Its molecular weight is 194.19 g/mol.

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Question 1: Which of the following statement is false about conjugated systems?

valkas [14]

Answer:

A conjugated system can only contain two alkenes: False

B. A cumulated diene is less stable than an isolated diene.

False

Explanation:

A. A conjugated system is more stable than an unconjugated system.: True

Due to resonance a conjugated system is more stable.

B. The s-trans isomer is favored over the s-cis isomer.: True

Due to repulsion in s-cis isomer they are less stable.

C. A conjugated system has multiple resonance structures. True

This is the reason they are stable.

D. A conjugated system can only contain two alkenes: False

A conjugated system may have may alternate double and triple bonds.

2) A trans alkene releases less heat upon hydrogenation than a cis alkene.

True

Trans alkenes are more stable than cis alkene. Thus heat of hydrogenation of trans alkene is less than cis alkene.

B. A cumulated diene is less stable than an isolated diene.

False

C. Multiple products can always form when treated a conjugated diene with HBr. True

There can be 1,2 or 1,4 addition

D. Conjugated systems arise only between sp2-hybridized atoms.

True

Conjugation allows resonance which is possible in sp2 systems

E. Conjugated double bonds involve unhybridized p-orbitals aligned with each other

True

The double bond is formed as pi bond due to side ways overlapping of unhybridized p orbitals

8 0

3 years ago

A metal foil has a threshold frequency of 5.45 \times 10^{14} \text{ } \text{Hz}5.45Ã—10 14 Hz. Which of the colors of visible l

nalin [4]

Answer:

Green, Blue, Indigo, Violet

Explanation:

According to Einstein's equation of photoelectric effect, the kinetic energy of emitted photoelectron is the difference between the energy of the incident photon and the work function of the metal. The work function of the metal referee to the minimum energy that must be supplied in order to eject an electron from a metal surface. The energy of the incident photon must exceed the work function of the metal.

When we look at the electromagnetic spectrum, only the selected colours have frequency above the threshold frequency as shown by the image attached below.

7 0

3 years ago

Read 2 more answers

Medicine and urine are seperated by which method?

vovikov84 [41]

Answer:

Screening for the presence of drugs in serum and urine using different separation modes of capillary electrophoresis. The most common mode is capillary zone electrophoresis (CZE), in which charged analytes migrate in a buffer under the influence of an electric field.

Explanation:

7 0

3 years ago

Which of the following variations would increase the force experienced by the egg upon landing? Select all that apply.

Svetlanka [38]

D the drop height would

3 0

4 years ago

How many moles of Na₂CO₃ required to create 9.54 liters of a 3.4 M solution

GarryVolchara [31]

Answer:

The answer to your question is 32.44 moles

Explanation:

Data

moles of Na₂CO₃ = ?

volume = 9.54 l

concentration = 3.4 M

Formula

Molarity = $\frac{number of moles}{volume}$

Solve for number of moles

number of moles = Molarity x volume

Substitution

Number of moles = (3.4)( 9.54)

Simplification

Number of moles = 32.44

3 0

3 years ago

Read 2 more answers