A percent composition is a percentage of a compound in a sample expressed as a fraction of the whole sample.

Answer:Hess's law states that the change of enthalpy in a chemical reaction (i.e. the heat of reaction at constant pressure) is independent of the pathway between the initial and final states. ... Hess's law allows the enthalpy change (ΔH) for a reaction to be calculated even when it cannot be measured directly.

Explanation:

3 0

3 years ago

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If you combine 230.0 mL of water at 25.00 ∘ C and 140.0 mL of water at 95.00 ∘ C, what is the final temperature of the mixture?

IgorLugansk [536]

Answer: The final temperature of the mixture is 51.49°C

Explanation:

When two samples of water are mixed, the heat released by the water at high temperature will be equal to the amount of heat absorbed by water at low temperature

$Heat_{\text{absorbed}}=Heat_{\text{released}}$

The equation used to calculate heat released or absorbed follows:

$Q=m\times c\times \Delta T=m\times c\times (T_{final}-T_{initial})$

$m_1\times c\times (T_{final}-T_1)=-[m_2\times c_2\times (T_{final}-T_2)]$ ......(1)

where,

q = heat absorbed or released

$m_1$ = mass of water at high temperature = 140 g (Density of water = 1.00 g/mL)

$m_2$ = mass of water at low temperature = 230 g

$T_{final}$ = final temperature = ?°C

$T_1$ = initial temperature of water at high temperature = 95.00°C

$T_2$ = initial temperature of water at low temperature = 25.00°C

c = specific heat of water= 4.186 J/g°C

Putting values in equation 1, we get:

$140\times 4.186\times (T_{final}-95)=-[230\times 4.186\times (T_{final}-25)]$

$T_{final}=51.49^oC$

Hence, the final temperature of the mixture is 51.49°C

5 0

4 years ago

Can someone help me? I don't know the answer and I need a justification for why the correct answer is correct

pav-90 [236]

Answer:

(A) The value of Kc for this reaction increases as temperature increases, because the reaction is endothermic.

Step-by-step explanation:

N₂O₄ ⇌ 2NO₂

colourless reddish-brown

NO₂ is a reddish-brown gas, while N₂O₄ is colourless.

When you cooled the sample to 0 °C, the position of equilibrium shifted to form more N₂O₄, that is, it shifted to the left.

According to Le Châtelier's Principle, when a stress is applied to a system at equilibrium, the system will respond in a way that tends to relieve the stress.

You applied a stress: you removed heat from the system. It responded by shifting in the direction that produces more heat (to the left).

If you consider heat as part of the reaction, the equation must be

N₂O₄ + heat ⇌ 2NO₂

The reaction is endothermic.

Furthermore, since the position of equilibrium shifted in the direction of reactants, the equilibrium constant decreased.

The value of K decreases as the temperature decreases. If we say it the other way, the value of K increases as the temperature increases.

The correct answer is (A) The value of Kc for this reaction increases as temperature increases, because the reaction is endothermic.

(B) and (D) are wrong, because the reaction is endothermic.

(C) is wrong, because the value of Kc decreases as temperature decreases.

7 0

3 years ago