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4 years ago

Which of the following processes is exothermic?

Chemistry

2 answers:

Elodia [21]4 years ago

8 0

Answer:

a. The reaction associated with DHºf for an ionic compound

Explanation:

An exothermic process is a process that loses heat for the surroundings, so the temperature of the system must decrease, and ΔH must be negative.

DHºf or ΔHºf of an ionic compound is always negative because the final energy is always lower than the initial. It happens because of the stability of the bond, the system wants a lower energy state to be stable.

The ionization of a lithium atom occurs with the gain of energy, which is given to the electron, so it may give off the atom. So it's an endothermic process.

To change the state of a solid to a gas (sublimation), the compound must gain heat, its temperature must increase, so it's always an endothermic process.

To break a covalent bond it's necessary the gain of energy, so it's an endothermic process.

Korvikt [17]4 years ago

5 0

Answer:A

Explanation:

The enthalpy change of formation for an ionic compound is calculated from the Born-Haber cycle. Using the Hess law of constant heat summation. The result is always negative (exothermic) because energy is given out when the new lattice is formed.

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What is the overall charge of an atom with 18 protons, 18 neutrons, and 19 electrons?

Charra [1.4K]

Answer:

as no. of protons is equals to the no. of electrons so, it is a neutral atom.

but, as Atomic No. = Mass No. - No. of neutrons

Atomic No. = No. of protons = 18

so, Mass No. = Atomic No. + No. of Neutrons= 18 + 20 = 38

so, correct option is C.

Explanation:

8 0

3 years ago

1. What is an isomer? How many possible isomers of hexane are there? What are the structural differences between these isomers?

UNO [17]

When two compounds have same molecular formula but different structural formula, they are said to be isomers of each other and this phenomenon is called as isomerism.

Hexane has six isomers.

The isomers of hexane have a difference in their structure due to parent chain length (chain isomerism). They are also differentiated on the basis of straight chain as in n-hexane and branched chain as in remaining five. Structures along with names are shown below.

8 0

3 years ago

The Earth's surface is colder than the air above it, what will happen to the air?

Nitella [24]

Answer:

If the earth's surface is cold, warm air above it will lose heat energy to the cold surface below and the now cool air will remain close to the surface. If a damp surface is warmer than the air above it, some water will evaporate, and the air above the surface will be heated.

Explanation:

7 0

3 years ago

How many moles would be in 85.OmL of 0.750M KOH?

Harlamova29_29 [7]

Answer: There are 0.0637 moles present in 85.0 mL of 0.750 M KOH.

Explanation:

Given: Volume = 85.0 mL (1 mL = 0.001 L) = 0.085 L

Molarity = 0.750 M

It is known that molarity is the number of moles of solute present in liter of a solution.

Therefore, moles present in given solution are calculated as follows.

$Molarity = \frac{moles}{Volume (in L)}\\0.750 M = \frac{moles}{0.085 L}\\moles = 0.0637 mol$

Thus, we can conclude that there are 0.0637 moles present in 85.0 mL of 0.750 M KOH.

7 0

3 years ago

Are there any vegetarian Italian Sausages?

Flura [38]

Yes, there are vegetarian italian sausages. One example is the Satanic sausage, which is prepared from dough, beans, spices, tomato, yeast, etc. But, yes, majority or I would say almost all of the Italian sausages are non-vegetarian sausages itselves.

6 0

3 years ago