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Romashka-Z-Leto [24]
2 years ago
15

Caffeine, a molecule found in coffee, tea, and certain soft drinks, contains C, H, O, and N. Combustion of 10.0 g of caffeine pr

oduces 18.13 g of CO₂, 4.639 g of H₂O, and 2.885 g of N₂. Determine the molar mass of the compound if it is between 150 and 210 g/mol.
Chemistry
1 answer:
denis-greek [22]2 years ago
8 0

Answer:

194 g/mol.

Explanation:

Hello,

In this case, one first must compute the mass of each element as shown below:

C=18.13gCO_2*\frac{12gC}{44gCO_2} =4.945gC\\H=4.639gH_2O*\frac{2.016gH}{18.0152gH_2O}=0.519gH\\N=2.885gN_2\\O=10.0g-4.945g-0.519g-2.885g=1.651gO

Next, the corresponding moles:

C=4.945gC*\frac{1molC}{12gC}=0.412mol\\H=0.519gH*\frac{1molH}{1gH}=0.519mol\\N=2.885gN*\frac{1molN}{14gN}=0.206molN\\O=1.648gO*\frac{1molO}{16gO} =0.103molO

Then, each element's subscripts is found to be:

C=\frac{0.412}{0.103}=4\\H=\frac{0.519}{0.103}=5\\N=\frac{0.206}{0.103} =2\\O=\frac{0.103}{0.103}=1

Therefore, the empirical formula is:

C_4H_5N_2O

Nonetheless, it has a molar mass of 97bg/mol, thereby, by multiplying such formula by 2 one gets:

C_8H_10N_4O_2

Which has a molar mass of 194 g/mol being correctly contained in the given interval.

Best regards.

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Licemer1 [7]

Answer:

a.)  

To warm the liquid from 35°C to 78°C:

(2.3 J/g-K) x (42.0 g) x (78 - 35) = 4154 J

To vaporize the liquid at 78°C:

(38.56 kJ/mol) x (42.0 g C2H5OH / 46.06867 g C2H5OH/mol) = 35.154 kJ

Total:

4.154 kJ + 35.154 kJ = 39.3 kJ

b.)  

To warm the solid from -155°C to -114°C:

(0.97 J/g-K) x (42.0 g) x (-114°C - (-155°C)) = 1670 J

To melt the solid at -114°C:

(5.02 kJ/mol) x (42.0 g C2H5OH / 46.06867 g C2H5OH/mol) = 4.5766 kJ  

To warm the liquid from -114°C to 78°C:

(2.3 J/g-K) x (42.0 g) x (78 - (-114)) = 18547 J

To vaporize the liquid at 78°C:

35.154 kJ  (as in part a.)

Total:

1.670 kJ + 4.5766 kJ + 18.547 kJ + 35.154 kJ = 59.9 kJ

Explanation:

8 0
2 years ago
Classify the following as qualitative or quantitative statements, giving your reasons. (a) The sun is approximately 93 million m
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Answer:

a) quantitative

b) qualitative

c) quantitative

d) qualitative

e) quantitative

Explanation:

a) it is a quantitative statement, since it uses the concepts of limits and aproxximation in the calculation to give its estimate.

b) it's a qualitative statement, beacause its an appreciation of someone who thinks that one's work ist better than another's.

c) it is a quantitative statement, since it is an expression that is mathematically demonstrated,

d) it's a qualitative, beacuse it'a a simple opinion of someone.

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What volume (ml) of a 0.2450 m koh(aq) solution is required to completely neutralize 55.25 ml of a 0.5440 m h3po4(aq) solution?
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5 0
2 years ago
Select all the correct answers.
nevsk [136]

Answer:

The energy gained by the peas is lost by the water;

Energy is transferred from the fire to the pot, then to the water, and then to the peas

Explanation:

According to the fundamental laws of thermodynamics, heat flows from hotter objects to colder ones.

Let's analyze the heat flow in each of the systems we have:

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  • Frozen peas are added to the hot water. We have a system of peas/water. In this scenario, water is hot. Thus, heat flows from water to peas (heat is lost by water and gained by peas).

Analyzing the answer choices, firstly we notice that the energy gained by the peas is lost by the water, as water is hotter than the peas. Hence, this is true.

Secondly, the peas gain energy, as energy is a synonym to heat. This means the fact that peas lose energy is false.

Thirdly, it's false to claim that energy is transferred from the peas to the water and the pot, as we actually have a reverse process: both pot and water are at a higher temperature and heat flows from them towards the peas at a lower temperature.

Fourthly, it's also false to claim that the water receives energy both from the ire and from the frozen peas: the water only gains energy from the fire that is at a higher temperature, but it loses energy to the frozen peas, as the water is hotter than the peas.

Finally, it's true that energy is transferred from the fire to the pot, then to the water, and then to the peas. This is simply understood knowing that the fire here is at the highest temperature and it directly interacts with the pot which transfers energy to the water. The water is now at a higher temperature relatively to the peas, so it transfers energy to the peas afterwards.

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Hydroxylammonium nitrate in water: HONH₃NO₃(aq) → OHNH₃⁺(aq) + NO₃⁻(aq).
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H⁺(aq) + HONH₂(aq) ⇄ HONH₃⁺(aq).
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8 0
2 years ago
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