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3 years ago

Select all of the following equations that represent an exothermic reaction.

1 answer:

3 0

Exothermic reactions:

1) release heat to the surroundings

2) the change of enthalpy, ΔH, is negative: ΔH < 0

3) the temperature of the system increases

With that you can conclude about every equation given:

NH3(g) + 12.0 kcal → ½N2(g) + 3/2 H2(g) : is not exothermic because heat in the side of the reactants means that heat is being used, not released.

C(graphite) → C(diamond), ΔH = - 0.45 kcal : is exothermic because ΔH is negative

C + 2S → CS2, ΔH = 27,550 cal: is not exothermic because ΔH is positive

CH4 + 2O2 → CO2 + 2H2O + 212,800 cal : is exothermic because heat appears as a product of the reaction, which means that it is released.

2H2O → 2H2 + O2, ΔH = +58 kcal : is not exothermic because ΔH is positive.

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3 years ago

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amid [387]

I think it would be c

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3 years ago

Using the Bohr model, determine the energy, in joules, necessary to ionize a ground-state hydrogen atom. Show your calculations.

lord [1]

Answer:

The energy required to ionize the ground-state hydrogen atom is 2.18 x 10^-18 J or 13.6 eV.

Explanation:

To find the energy required to ionize ground-state hydrogen atom first we calculate the wavelength of photon required for this operation.

It is given by Bohr's Theory as:

1/λ = Rh (1/n1² - 1/n2²)

where,

λ = wavelength of photon

n1 = initial state = 1 (ground-state of hydrogen)

n2 = final state = ∞ (since, electron goes far away from atom after ionization)

Rh = Rhydberg's Constant = 1.097 x 10^7 /m

Therefore,

1/λ = (1.097 x 10^7 /m)(1/1² - 1/∞²)

λ = 9.115 x 10^-8 m = 91.15 nm

Now, for energy (E) we know that:

E = hc/λ

where,

h = Plank's Constant = 6.625 x 10^-34 J.s

c = speed of light = 3 x 10^8 m/s

Therefore,

E = (6.625 x 10^-34 J.s)(3 x 10^8 m/s)/(9.115 x 10^-8 m)

E = 2.18 x 10^-18 J

E = (2.18 x 10^-18 J)(1 eV/1.6 x 10^-19 J)

E = 13.6 eV

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3 years ago

The positive sign of the energy difference in a chemical reaction would indicate that ..........

trasher [3.6K]

Answer:

B) the chemicals are gaining energy from the surroundings.

Explanation:

The positive sign of the energy difference in a chemical reaction would indicate that the chemicals are gaining energy from the surroundings. This is what happens in an endothermic reaction.

In an endothermic reaction, heat is absorbed from the surroundings hence the surrounding becomes colder at the end of the changes.

Here the energy change is assigned a positive value.
This is because the heat energy level of the final state is higher than that of the initial state.
So, the difference gives a positive value.

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2 years ago

To fulfill the octet rule electron sharing leads to ____ electrons around each atom?

Dimas [21]

D. 8

You can predict it from it's name "Octet" means Eight. Atom must have that number of electron to have a stable structure!

Hope this helps!

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3 years ago

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