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Jlenok [28]
3 years ago
9

Evidence of a chemical change would be

Chemistry
2 answers:
Elodia [21]3 years ago
4 0
D- Rusting car fender
Charra [1.4K]3 years ago
4 0
ANSWER: D) rusting car fender
HOPE THIS HELPS
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Approximately how many particles are in 2 moles?
schepotkina [342]

Answer:

1.2\times10^2^4 particles in 2 moles.

Explanation:

The number of particles that are contained in one mole, the international unit of amount of substance: by definition, exactly 6.022×10²³, and it is dimensionless. It is named after the scientist Amedeo Avogadro.

It is also known as Avogadro's constant.

∴ Number of particles in one mole = 6.022\times10^2^3

∴ Number of particles in 2 mole = 2 times Number of particles in one mole

∴ Number of particles in 2 mole=2\times6.022\times10^2^3=12.044\times10^2^3\approx1.2\times10^2^4

Hence there are 1.2\times10^2^4 particles in 2 moles.

4 0
2 years ago
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An element has an atomic number of 30. How many protons and electrons are in a neutral atom of the element? A. 30 protons, 30 el
Minchanka [31]
Atomic number shows the number of protons in an atom's nucleus. If the atomic number is 30, then it has 30 protons. The question says it is neutral, so it must have the same amount of protons and electrons.

A is the correct answer based on this. 
7 0
3 years ago
A scientist makes several observations, develops a question, researches what is known about the question, forms a hypothesis, an
Alex73 [517]
The scientist should make a new hypothesis and do a new experiment! That is what I say!
8 0
3 years ago
CalcuLate the velocity of an electron ejected if 300.0 mm of light is applied to the surface. A wavelength of 795 nm has suffici
worty [1.4K]
The equation relating velocity and wavelength is written below:

v = λf
where λ is the wavelength in m while f is frequency in 1/s.

Let's determine first the frequency from the speed of light:
c = distance/time, where c is the speed of light equal to 3×10⁸ m/s
3×10⁸ m/s = (300 mm)(1 m/1000 mm)/ time
time = 1×10⁻⁹ seconds
Since f = 1/t,
f = 1/1×10⁻⁹ seconds = 10⁹ s⁻¹

Thus,
v = (795×10⁻⁹ m)(10⁹ s⁻¹)
v = 795 m/s
8 0
2 years ago
How is iron extracted? Describe in brief​
Feliz [49]

Answer:Iron is extracted from iron ore in a huge container called a blast furnace. Iron ores such as haematite contain iron(III) oxide, Fe 2O 3. The oxygen must be removed from the iron(III) oxide in order to leave the iron behind. Reactions in which oxygen is removed are called reduction reactions.

3 0
3 years ago
Read 2 more answers
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