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konstantin123 [22]
3 years ago
10

Select the correct answer. When Phillip analyzed an unknown substance X, he found that it contained only one kind of atom. Phill

ip was unable to convert the substance to a simpler one. What is substance X? A. a compound B. an element C. a heterogeneous mixture D. a homogeneous mixture
Chemistry
1 answer:
mash [69]3 years ago
7 0

The correct answer is option B, that is, an element.  

A compound comprises of either more than one kind of atom or various similar atoms. They can be dissociated or can be converted into a simpler one. An element refers to a substance that comprises only one kind of atom. It cannot be dissociated further or can be converted into simpler substance by any chemical means.  

Heterogeneous mixture refers to a non-uniform mixture of distinct atoms without any chemical bonding in between them. On the other hand, homogenous mixture refers to a uniform mixture of distinct atoms with the absence of any kind of chemical bonding in between them.  


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1.5 moles of Al is how many<br> atoms?
aev [14]

Answer:

<h2>9.03 × 10²³ atoms </h2>

Explanation:

The number of atoms of Al can be found by using the formula

<h3>N = n × L</h3>

where n is the number of moles

N is the number of entities

L is the Avogadro's constant which is

6.02 × 10²³ entities

From the question we have

N = 1.5 × 6.02 × 10²³

We have the final answer as

<h3>9.03 × 10²³ atoms</h3>

Hope this helps you

4 0
3 years ago
A 20 kg curling stone is sliding in a positive direction at 4 m/s. A second curling stone is sliding at the same speed but in th
solniwko [45]

Answer:

The kinetic energy of the two stones is 320 J

Explanation:

Kinetic energy is the energy that a body possesses due to its movement. So it is the capacity or work that allows an object to go from being at rest, or still, to moving at a certain speed.

In other words, the kinetic energy of an object is that which is produced due to its motion and depends on its mass and velocity as follows:

Ec=\frac{1}{2} *m*v^{2}

where the kinetic energy Ec is measured in joules (J), the mass m is measured in kilograms (kg) and the velocity v in meters/second (m/s).

In this case you know that a 20 kg curling stone is sliding in a positive direction at 4 m/s. So:

  • m= 20 kg
  • v= 4 m/s

Replacing you have:

Ec_{1} =\frac{1}{2} *20 kg*(4\frac{m}{s}) ^{2}

Ec₁= 160 J

A second curling stone slides at the same speed but in the opposite direction. So:

  • m= 20 kg
  • v= - 4 m/s

Replacing you have:

Ec_{2} =\frac{1}{2} *20 kg*(-4\frac{m}{s}) ^{2}

Ec₂= 160 J

The kinetic energy of the two stones is calculated as:

Ec= Ec₁ + Ec₂

Ec= 160 J + 160 J

Ec= 320 J

<u><em>The kinetic energy of the two stones is 320 J</em></u>

7 0
3 years ago
By using the following reactions, calculate the heat of formation of pentane (C5H12) gas from carbon and hydrogen gas. C (s) + O
Llana [10]

Answer: ΔH = 145 kJ/mol


Explanation:


1) Equations given:


C (s) + O₂ (g) → CO₂ (g), ΔH = 395 kJ/mol


H₂ (g) + 1/2O₂ (g) → H₂O (l), ΔH = 285 kJ/mol


C₅H₁₂ (g) + 8O₂ → 5CO₂ (g) + 6H₂O (l), ΔH = 3.54 × 10³ kJ/mol


2) Target equation:


5C(s) +6 H₂(g) → C₅H₁₂(g)


3) Hess law


As per Hess law you can handle the chemical equations (add, subtract, reverse, multiply by a coefficient) to find the target equation, and then the net sum of the heat changes of the individual reactions equals the heat change of the target reaction.


4) Now, you must figure out how to transform the individual reactions to end up with the final equation:


Here is how:


i) Multiply the first one by 5:


5C (s) + 5O₂ (g) → 5CO₂ (g), ΔH = 5×395 kJ/mol


ii) Multiply the second by 6:


6H₂ (g) + 3O₂ (g) → 6H₂O (l), ΔH = 6×285 kJ/mol


iii) Reverse the third:


5CO₂ (g) + 6H₂O (l) → C₅H₁₂ (g) + 8O₂ , ΔH = - 3.54 × 10³ kJ/mol


iv) Add them up:


5C (s) + 5O₂ (g) → 5CO₂ (g), ΔH = 5×395 kJ/mol


6H₂ (g) + 3O₂ (g) → 6H₂O (l), ΔH = 6×285 kJ/mol


5CO₂ (g) + 6H₂O (l) → C₅H₁₂ (g) + 8O₂ , ΔH = - 3.54 × 10³ kJ/mol

----------------------------------------------------------------------------------------------

5C (s) + 6H₂ → C₅H₁₂ (g),


ΔH = 5×395 kJ/mol + 6×285 kJ/mol - 3.54 × 10³ kJ/mol


⇒ ΔH = 145 kJ/mol

6 0
4 years ago
Read 2 more answers
A researcher is measuring changes in the density of the upper atmosphere over time. Which units should be used for the density m
valina [46]

Answer:

lbm/ft³ or psi/ft

Explanation:

The description in the question shows the density to measured is that of gases (upper atmosphere). The density of a gas can be described as the mass of the gas divided by the volume of the gas at a certain temperature and pressure. It's unit can be represented as lbm/ft³ or psi/ft.

NOTE:

"lbm" means "lean body mass" which is a unit for mass or weight and can be described as the pound mass

"psi" means "pound per square inch"; is also a unit for mass or weight

5 0
3 years ago
Which of the following has electrons in a d orbital?<br> Mg<br> Si<br> Cr<br> Са
erica [24]
Cr.
Cr is the only element listed that is located in the d-block of the periodic table.
6 0
3 years ago
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