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3 years ago

How is an exothermic reaction identified on a potential energy diagram?

1 answer:

4 0

Energy diagrams are use to depict the energy changes that occur during a chemical reaction. There are two types of reaction based on the energy change, these are exothermic and endothermic reactions. In endothermic reactions energy are gained while in exothermic reactions energy are lost to the environment. To identify an exothermic reaction on a potential energy diagram, one has to compare the potential energy of the reactants and the products. If the potential energy of the product is less than that of the reactants, the reaction is exothermic.

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The change in internal energy for the combustion of 1.0 molmol of octane at a pressure of 1.0 atmatm is -5084.1 kJkJ . Part A If

Dovator [93]

Answer:

W = -10.3 kJ

Explanation:

During combustion, the system performs work and releases heat. Therefore, the change in internal energy is negative, and the change in enthalpy, which is equal to heat at constant pressure, is also negative. Work is then calculated by rearranging the equation for the change in internal energy:

w=ΔE−qp=−5084.3 kJ−(−5074.0 kJ)

The release of heat is much greater than the work performed by the system on its surroundings. The potential energy stored in the bonds of octane explains why considerably large amounts of energy can be lost by the system during combustion.

3 0

3 years ago

Two liquids are analyzed and found to both be 85.7% carbon and 14.3% hydrogen. At 750 mmHg and 150 C, both are gases. At these c

vodomira [7]

Answer:

Molecular formula A: C₅H₁₀

Molecular formula B: C₇H₁₄

Explanation:

It is possible to obtain empirical formula of compounds using percent composition, thus:

C: 85.7% × (1mol / 12.01g) = 7.136 moles C

H: 14.3% × (1mol / 1.01g) = 14.158 moles H

Mole ratio of H:C is:

14.158mol / 7.136mol = 2

That means in compounds A and B you have 2 hydrogens per atom of carbon and empirical formila is:

CH₂

Using PV = nRT, moles of A and B are:

Where P is pressure (750mmHg / 760 = 0.987atm), V is volume (0.8000L), R is gas constant (0.082atmL/molK), and T is temperature (150°C +273.15 = 423.15K)

Moles A and B: n = PV / RT

n = 0.987atm×0.8000L / 0.082atmL/molK×423.15K

n = 0.0228 moles of A and B.

Using the mass of A and B it is possible to find molar mass of each compound:

A = 1.60g / 0.0228mol = 70.31g/mol

B = 2.22g / 0.0228mol = 97.56g/mol

As empirical formula of both compounds is CH₂, (molar mass = 14.03g/mol). Molecular formula of compounds is:

A = 70.31g/mol / 14.03g/mol = 5 → Molecular formula: 5×CH₂ = C₅H₁₀

B = 97.56g/mol / 14.03g/mol = 7 → Molecular formula: 7×CH₂ = C₇H₁₄

8 0

3 years ago

Explain the two main physical/ chemical processes by which carbon dioxide molecules in the air move to the cells of phytoplankto

VARVARA [1.3K]

Answer:

The two physical/ chemical processes by which carbon dioxide molecules in the air move to the cells of phytoplankton in the ocean are the photosynthesis and the biological carbon pump.

Explanation:

The biological carbon pump is the action of organisms to move carbon during chemical and biological interactions from the surface into the deeper ocean and then to rocks.

The biological carbon pump its composed of three processes, which are the photosynthesis, the gravity and the food web interactions. They are all part of the carbon cycle.

During the photosynthesis, the phytoplankton take up carbon dioxide from the atmosphere that is dissolved in the surface water, and receives the energy from the sun to turn it into glucose and oxygen.

In the cells of the phytoplankton, glucose is transformed into other organic compounds. This material has organic carbon that can end in two ways: it is incorporated to marine organisms during the food web interactions or it can be remineralised forming calcium carbonate in the ocean surface.

The remineralization can be done by many organisms to build its shells or skeletons, or by chemical processes that happen in the ocean. This process allows more carbon dioxide to enter the water and to continue the cycle.

So when marine organisms die, all its organic components sink into the bottom of the ocean and carbon-rich sediments are form. And after millions of years, these sediments turn into rocks after going through chemical and physical phenomenon.

3 0

3 years ago

Which chemical formula represents an organic molecule? A.CCl2F2 B.4H2O C.Al2O3 D.H2SO4

Irina18 [472]

Answer:

Explanation:

7 0

3 years ago

Read 2 more answers

Problem: Convert 30 cm to mm. Need full process pls help

marta [7]

Answer: 300mm

Explanation:

30cm x (10mm/1cm) x (1mm/1mm) = 300mm

Btw, I'm not sure about the (1mm/1mm).

3 0

3 years ago