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rosijanka [135]
3 years ago
13

what kind of evidence indicates a chemical change ?... a physical change? you may use examples to show softened.

Chemistry
1 answer:
SOVA2 [1]3 years ago
3 0
Some things that can indicate a chemical change are change of odor, change of color, change in temperature or energy, such as the production or loss of heat. An example could be the rusting of metal, there would be a color change of going from a shiny silver to a dirty, splotchy red color. Some things that indicate a physical change are change of appearance like change of shape, etc. It can also be like a change between a solid to liquid to gas. For example, the cutting of a piece of paper.
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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

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3 years ago
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Calculate the wavelength of a football (425g) thrown by an NFL quarterback traveling at 50mph
AnnyKZ [126]

Wavelength is 6.976 x 10^ -35 m

Explanation:

In this, we can use De Broglie’s equation. This equation is the relationship between De Broglie’s wavelength, velocity and the mass of a moving object. In this equation, we are using plank's constant which is 6.626 x 10^-34 m^2 kg/s.

We know that one mile per hour is equivalent to 0.447 M/S.

And One gram is equivalent to 10^-3 kg.

De Broglie’s wavelength = λ ( wave length) = Plank’s constant/ Mass x velocity

λ ( wave length) = 6.626 x 10^ -34/ (425 x10^-3) x ( 50 x 0.447)

                                 = 6.626 x 10^ -34/ 0. 425 x 22.35

                                 = 6.626 x 10^ -34/ 9.498

                                 = 6.976 x10^ -35 m

So, the wavelength of the football will be 6.976 x 10^ -35 m

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lbvjy [14]
The answer is A. True
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Explanation:

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