What is a pure substance? Element, compound, mixture

Chemistry

2 answers:

Alika [10]4 years ago

6 0

An Element is a pure substance.

AlekseyPX4 years ago

5 0

Elements are pure substances :)

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How many nitrogen atoms are present in 0.150 mol of zn(no3)2?

gregori [183]

First calculate number of Nitrogen atoms contained by 1 mole of Zn(NO₃)₂,

As one formula unit of Zn(NO₃)₂ contains 2 Nitrogen atoms, then one mole of Zn(NO₃)₂ will contain,

= 2 × 6.022 × 10²³

= 1.20 × 10²⁴ Atoms of Nitrogen / mole

Now, calculate number of Nitrogen Atoms in 0.150 moles of  Zn(NO₃)₂.
As,
1 mole of  Zn(NO₃)₂ contained = 1.20 × 10²⁴ atoms of N
Then,
0.15 mole of  Zn(NO₃)₂ will contain = X atoms of N
Solving for X,

X = (0.15 mol × 1.20 × 10²⁴ atom) ÷ 1 mol

X = 1.80 × 10²⁴ Atoms of Nitrogen
Result:
So, 0.15 mole of  Zn(NO₃)₂ contains 1.80 × 10²⁴ atoms of Nitrogen.

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3 years ago

A light strikes the boundary of a medium at a 45 degree angle. Instead of entering the second medium, the light reflects back in

Dahasolnce [82]

Answer:

D It must be equal to 1.00

Explanation:

The refraction in the second medium must be equal to 1. The refraction index is given as the ration of the angle of incidence to the angle of refraction. This is given as a fraction. In other words:

$\frac{sin\theta _{i} }{sin\theta _{r} } = n$

where Θ₁ and Θ₂ are angles of incidence an refraction, and n is the refractive index.

At a critical angle, the refraction is equal to the reflection inside the medium. This results in a phenomenon called total internal reflection where light is reflected internally in the medium.

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What stated of matter and how many phases are present when a 5.0 mL sample of oil is mixed with 100.0 mL of water?

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two layers of different liquids=two phases.

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Answer: