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3 years ago

When two or more substances are mixed together without undergoing a chemical reaction, it results in a/an?

2 answers:

6 0

The observable signs when a chemical reaction has occurred are either of the following:

*formation of precipitate
*formation of gas
*change in color

Otherwise, it is just a physical change. <em>When these two substances are mixed together, it results in a mixture. If these two substances are soluble with each other, then the mixture is specifically called a solution.</em>

erastova [34]3 years ago

4 0

Mixture.............

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From the values of ΔH and ΔS, predict which of the following reactions would be spontaneous at 28°C: reaction A: ΔH = 10.5 kJ/mo

Ainat [17]

Answer: A:

ΔH = 10.5 kJ/mol, ΔS = 30.0 J/K·mol is non-spontaneous.

ΔH = 1.8 kJ/mol, ΔS = −113 J/K · mol is non-spontaneous.

Reaction A can become spontaneous

Reaction A is spontaneous at 76.85 °C

Explanation:

It's helpful to memorize that if:

-ΔS is greater than 0 and ΔH is less than 0; its spontaneous at all temperatures.

-ΔS is less than 0 and ΔH is greater than 0; its non-spontaneous at all temperature.

-ΔS is greater than 0 and ΔH is greater than 0; its spontaneous at high temperatures and non-spontaneous at low temperatures.

-ΔS is less than 0 and ΔH is less than 0; its spontaneous at low temperatures and non-spontaneous at high temperatures.

This comes from the equation ΔG=ΔH-TΔS

where ΔG is Gibbs free energy, ΔH is enthalpy, T is temperature (in Kelvin), and ΔS is entropy.

Without getting too in depth as to what each of those mean (you could take an entire class on entropy alone), the temperature at which the spontaneity changes is equal to ΔG (Gibbs free energy) at 0.

So take the above equation and set ΔG = 0, and rearrange the equation to solve for T.

ΔG=ΔH-TΔS

0=ΔH-TΔS

add TΔS to the other side

TΔS=ΔH

divide the right side by ΔS to find T (temperature)

T=ΔH/ΔS

Now we can find the temperature that the first reaction would occur at spontaneously.

We need to make sure that we have the same units for ΔH and ΔS, so divide 30 by 1000 to convert J/Kmol into kJ/kmol so that we have kJ for ΔH and ΔS.

30/1000 = 0.03 kJ

Plug in the values for the modified equation T=ΔH/ΔS

10.5 kJ/0.03 kJ = 350 K

The temperature is in Kelvin, so subtract 273.15 to convert it into Celsius

350-273.15 = 76.85 °C

7 0

4 years ago

Read 2 more answers

The rate of disappearance of HBr in the gas phase reaction 2HBr(g)→H2(g)+Br2(g) is 0.190 Ms−1 at 150 ∘C. The rate of reaction is

nydimaria [60]

Answer:

Rate of reaction is $0.0950M.s^{-1}$

Explanation:

Applying law of mass action for this reaction: $rate=-\frac{1}{2}\frac{\Delta [HBr]}{\Delta t}=\frac{\Delta [H_{2}]}{\Delta t}=\frac{\Delta [Br_{2}]}{\Delta t}$
$-\frac{\Delta [HBr]}{\Delta t}$ represents rate of disappearance of HBr, $\frac{\Delta [H_{2}]}{\Delta t}$ represents rate of appearance of $H_{2}$ and $\frac{\Delta [Br_{2}]}{\Delta t}$ represents rate of appearance of $Br_{2}$
Here, $-\frac{\Delta [HBr]}{\Delta t}=0.190M.s^{-1}$
So, rate of reaction = $\frac{1}{2}\times (0.190M.s^{-1})=0.0950M.s^{-1}$

6 0

3 years ago

A student must make a 3 m acid solution using a 5 m acid solution. which of these is the safest way to make the solution?

weqwewe [10]

The motivation to abstain from adding water to concentrated acids is that, with a few acids, amid weakening, a considerable measure of warmth is discharged, by adding the corrosive to the water, the generally extensive measure of water will retain the warmth. On the off chance that you added water to concentrated corrosive when you initially beginning pouring the water, it could get sufficiently hot for the little measure of water that was filled all of a sudden bubble and splatter corrosive on you. Concentrated sulfuric corrosive is most famous for doing this, not all acids get that hot on weakening, but rather in the event that you make a propensity for continually adding the corrosive to water for every one of them, you can't turn out badly.

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4 years ago

Tropical fish owners must keep the water in the tank from getting too warm or the fish will die. Why is this true?1.) There is t

Irina-Kira [14]

Option 4 or the dissolution of the oxygen decreases

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4 years ago

Explain the reactivity of the Nobel gases in terms of valence electrons

kirill115 [55]

Noble gases are the least reactive of all elements because they have 8 valence electrons which fill their outer energy level. Having 8 valence electrons is the most stable arrangement of electrons, thus, Noble gases rarely react with other elements.

8 0

3 years ago