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Leokris [45]
3 years ago
8

Which of the following observations is usually not evidence of a chemical change ?

Chemistry
1 answer:
Nookie1986 [14]3 years ago
5 0

Answer:

D

Explanation:

Have a nice day

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The rate constant of a certain reaction is known to obey the Arrhenius equation, and to have an activation energy . If the rate
vovangra [49]

Answer:

K2 = 61.2 M^-1.S^-1

Explanation:

We complete the question fully:

The rate constant of a certain reaction is known to obey the Arrhenius equation, and to have an activation energy Ea = 71.0kJ/mol . If the rate constant of this reaction is 6.7M^(-1)*s^(-1) at 244.0 degrees Celsius, what will the rate constant be at 324.0 degrees Celsius?

Answer is as follows:

The question asks us to calculate the value of the rate constant at a certain temperature, given that it is at a particular value for a particular temperature. We solve the question as follows:

According to Arrhenius equation, the relationship between temperature and activation energy is as follows:

            k = Ae^-(Ea/RT)

where,   k = rate constant

              A = pre-exponential factor

          Ea  = activation energy

             R = gas constant

              T = temperature in kelvin

From the equation, the following was derived for a double temperature problem:

ln(k2/k1) = (-Ea/R) * (1/T1 - 1/T2)

We list out the parameters as follows:

         

      T1= (244 + 273.15) K = 517.15 K

      T2= (324+ 273.15) K =597.15 K

    K1  = 6.7 ,     K2 = ?

         R = 8.314 J/mol K

     Ea = 71.0 kJ/mol = 71000 J/mol

Putting the given values into the above formula as follows:

ln(k2/6.7) = (-71000/8.314) * (1/517.15 - 1/597.15)

lnk2 - 1.902 = 8539.8 * 0.000259

lnK2 = 1.902 + 2.21

lnK2 = 4.114

K2 = e^(4.114)

K2 = 61.2

Hence, K2 = 61.2 (M.S)^-1

7 0
3 years ago
Read 2 more answers
A tank is filled with gasoline to a depth of exactly 2 feet. The tank is a cylinder resting horizontally on its side, with its c
inna [77]

Answer:

The volume of the gasoline in the tank is 18.85 cubic feet

Explanation:

The tank is a cylinder. The equation for calculating the cylinder volumen is πr²*h, r is radius and h is height. π is approximately 3.1416. So,  The tank is  resting horizontally on its side, its radius is 2 feet/2= 1 feet. h=a tank long= 6 feet.

With equation:

Vol gasoline=3.1416*1²*6=18.85 feet ³

I hope my answer helps you

6 0
3 years ago
A 248-g piece of copper is dropped into 390 mL of water at 22.6 °C. The final temperature of the water was measured as 39.9 °C.
max2010maxim [7]

Answer:

The answer to your question is: Initial temperature of copper = 67.1°C

Explanation:

Data

mass Copper = 248 g

volume Water = 390 ml

T1 water = 22.6°C

T2           = 39.9°C

T1 copper = ?

Specific heat water = 1 cal/g°C

Specific heat copper = 0.092 cal/g°C

Formula       copper             water

Heat is negative for copper because it releases heat

                  - mCp(T2 - T1) = mCp(T2 - T1)                  

                  - (248)(39.9 - T1) = 390 (1)((39.9 - 22.6)           Substitution

                 -9895.2 + 248T1 = 390(17.3)                             Simplification

                 -9895.2 + 248T1 = 6747

                 248 T1 = 6747 + 9895.2

                 248 T1 = 16642.2

                 T1 = 16642.2 / 248

                 T1 = 67.1 °C                                                         Result

6 0
3 years ago
Send Message
Ganezh [65]

Answer:

1 Atm

Explanation:

Dalton's law

The total pressure is 3 Atm so all you have to do is subtract the other partial pressures from 3

4 0
3 years ago
Read 2 more answers
Elaborate on how to classify elements and pure compounds.
tankabanditka [31]

Answer: C) Elements and pure compounds are homogeneous materials because they have a uniform composition throughout.

Explanation: Element is a pure substance which is composed of atoms of similar elements. Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.

Elements are compounds form homogeneous materials as they have uniform composition throughout and the components are evenly distributed throughout the material.

Mixtures are heterogeneous materials as they do not have uniform composition and the components are not evenly distributed throughout the material.

4 0
3 years ago
Read 2 more answers
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