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Zinaida [17]
3 years ago
10

The pile of ash left after a fire burns out demonstrates what concept? A. Original materials remain after a physical change. B.

A chemical change forms new substances. C. Physical properties are never stable. D. Fire recycles most substances.
Chemistry
1 answer:
Nana76 [90]3 years ago
5 0
The answer is A original materials remain after a physical.
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If the visible light spectrum is from 400 to 700 nm, would light with an energy of 2.79 x 10^-19 J be visible with the naked eye
sladkih [1.3K]

Answer:

713 nm. It is not visible with the naked eye.

Explanation:

Step 1: Given data

  • Energy of light (E): 2.79 × 10⁻¹⁹ J
  • Planck's constant (h): 6.63 × 10⁻³⁴ J.s
  • Speed of light (c): 3.00 × 10⁸ m/s
  • Wavelength (λ): ?

Step 2: Calculate the wavelength of the light

We will use the Planck-Einstein equation.

E = h × c / λ

λ = h × c / E

λ = 6.63 × 10⁻³⁴ J.s × 3.00 × 10⁸ m/s / 2.79 × 10⁻¹⁹ J

λ = 7.13 × 10⁻⁷ m

Step 3: Convert "λ" to nm

We will use the relationship 1 m = 10⁹ nm.

7.13 × 10⁻⁷ m × (10⁹ nm/1 m) = 713 nm

This light is not in the 400-700 nm interval so it is not visible with the naked eye.

5 0
3 years ago
Help RRLY EASY I JUST DONT UNDERSTAND
andreyandreev [35.5K]

Answer:

the first fill-in is 400

the second fill-in is 4

Explanation:

5 0
3 years ago
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Mercury can be obtained by reacting mercury(I) sulfide with calcium oxide. How many grams of calcium oxide are needed to produce
OLga [1]
First, 55 g of Hg is 3.65 moles because one mole of Hg has a molar mass of 200.59

Then, the mole ratio of Hg to CaO is 8:4 or 2:1. SO we divide 3.65 by 2 to get 1.82 moles of CaO

This is the same as 102.06 grams because one mole of CaO has a molar mass of 56.0774

Hope this helps!
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Is the soup saturated with salt at 20°C? Explain why or why not.
yKpoI14uk [10]
The salt doesn't dissolve at that temperature. heating aids in dissolving
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The scientific study of matter and the changes it undergoes is called
barxatty [35]
A. Chemistry
The scientific study of matter and the changes it undergoes is called chemistry

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