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hammer [34]
3 years ago
9

Which of the changes are chemical changes?

Chemistry
1 answer:
puteri [66]3 years ago
7 0

A chemical change results from a chemical reaction, while a physical change is when matter changes forms but not chemical identity. Examples of chemical changes are burning, cooking, rusting, and rotting. Examples of physical changes are boiling, melting, freezing, and shredding.
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What organ system carries oxygen and food aoround the body for respiration
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2 years ago
What is the molecular formula of first 20 elements​
attashe74 [19]

Answer:

H

He

Li

Be

B

C

N

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F

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Mg

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3 years ago
A small can rolled 2 meters in 2 hours.​
inn [45]
2.187 is the answer to this question
7 0
2 years ago
How many photons are produced in a laser pulse of 0.364 J at 477 nm?
Luda [366]

Answer:

1.00 × 10¹⁸

Explanation:

1. Calculate the <em>energy of one photon</em>

The formula for the energy of a photon is

<em>E</em> = <em>hc</em>/λ  

<em>h</em> = 6.626 × 10⁻³⁴ J·s; <em>c</em> = 2.998 × 10⁸ m·s⁻¹

λ = 477 nm = 477 × 10⁻⁹ m                              Insert the values

<em>E</em> = (6.626 × 10⁻³⁴ × 2.998× 10⁸)/(477 × 10⁻⁹)

<em>E</em> = 4.165× 10⁻¹⁹ J

2. Calculate the <em>number of photons</em>

Divide the total energy by the energy of one photon.

No. of photons = 0.418 × 1/4.165 × 10⁻¹⁹      

No. of photons = 1.00 × 10¹⁸

7 0
3 years ago
Calculate the pH of a solution created by placing 2.0 grams of yttrium hydroxide, Y(OH)3, in 2.0 L of H2O. Ksp for Y(OH)3 is 6.0
oee [108]

Answer:

pH = 8.314

Explanation:

  • Y(OH)3(s) ↔ Y+  +  3OH-

equil:   S               S         3S

∴ Ksp = [ Y+ ] * [ OH- ]³ = 6.0 E-24

⇒ 6.0 E-24 = ( S )*( 3S )³

⇒ 6.0 E-24 = 27S∧4

⇒ 2.22 E-25 = S∧4

⇒ ( 2.22 E-25 )∧(1/4) = S

⇒ S = 6.866 E-7 M

⇒ [ OH- ] = 3*S =2.06 E-6 M

⇒ pOH = - Log [ OH- ]

⇒ pOH = - Log ( 2.06 E-6 )

⇒ pOH = 5.686

∴ pH = 14 - pOH

⇒ pH = 8.314

8 0
3 years ago
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