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3 years ago

True or false

Chemistry

1 answer:

sweet-ann [11.9K]3 years ago

8 0

Answer:

True.

But it only changes in physical change.

How?

Explanation:

The chemical reaction produces a new substance with new and different physical and chemical properties. Matter is never destroyed or created in chemical reactions. The particles of one substance are rearranged to form a new substance.

In a physical change, a substance's physical properties may change.

A chemical change is a permanent change. A Physical change affects only physical properties i.e. shape, size, etc. ... Some examples of physical change are freezing of water, melting of wax, boiling of water, etc. A few examples of chemical change are digestion of food, burning of coal, rusting, etc.

Hope this helps!

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Calculate the maximum KE and velocity of an electron from zinc by a 275nm photon

Dmitry [639]

Answer:

Kinetic energy: $6.024*10^{-20}$

Velocity: $3.64*10^{5}$

Explanation:

From the equations of the photo-electric effect,

We know:

$hv=hv_0+K.E$

Where,

1. $h$ is the Planck's constant which is $6.626*10^{-34}$

2. $v,v_0$ are the frequency of light emitted and threshold frequencies respectively.

3. $K.E$ is the kinetic energy of the electrons emitted.

By fact, we come to know that the threshold frequency of Zn is 300nm

And also $v=\frac{c}{d}$

Where ,

1. $c$ is the speed of light $=3*10^8$

2. $d$ is the wavelength.

Thus,

$\frac{hc}{d}=\frac{hc}{d_0}+K.E\\K.E=\frac{hc}{d}-\frac{hc}{d_0}\\K.E=hc*(\frac{1}{d}-\frac{1}{d_0})\\K.E=6.626*10^{-34}*3*10^8*(\frac{1}{275*10^{-9}}-\frac{1}{300*10^{-9}})\\K.E=6.024*10^{-20}kgm^2s^{-2}$

Now to find velocity:

$K.E=\frac{1}{2}mv^2\\v^2=1.324*10^{11}\\v=3.64*10^5$

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3 years ago

Help me with number 19 and 20 please

Doss [256]

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3 years ago

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lubasha [3.4K]

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Explanation:

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dexar [7]

Answer:

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Explanation:

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