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Alenkinab [10]
2 years ago
12

An unknown substance is obtained by police. The forensics laboratory has

Chemistry
1 answer:
timurjin [86]2 years ago
5 0

Answer:

70.0 %

Explanation:

Step 1: Given data

  • Mass of nitrogen (mN): 74.66 g
  • Mass of the compound (mNxOy): 250 g

Step 2: Calculate the mass of oxygen (mO) in the compound

The mass of the compound is equal to the sum of the masses of the elements that form it.

mNxOy = mN + mO

mO = mNxOy - mN

mO = 250 g - 74.66 g = 175 g

Step 3: Determine the percent composition of oxygen in the sample

We will use the following expression.

%O = mO / mNxOy × 100%

%O = 175 g / 250 g × 100% = 70.0 %

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What common household element can, over time, reduce airflow, insulate components, reduce heat exchange or even cause the system
lina2011 [118]

Answer:

The correct answer is Dust

Explanation

Dust is a dry dirt in powder form usually found on surfaces of items in a building, it comprises of very small particles of soil, sand and sometimes includes toxic substances, skin cells,bacteria, soil particles, particles of clothing material, tiny pieces of dead insects and pollen

4 0
3 years ago
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In which situation is no work considered to be done by a force?
Masja [62]

If the angle is either 0 or 180, that means that there is either negative or positive work, so A and D are not correct.

If the angle is 45, then there is still some work involved.

The only option where there is no work done by a force is B. when the angle is between the force and displacement is 90. 

7 0
3 years ago
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A certain half-reaction has a standard reduction potential +0.80 V . An engineer proposes using this half-reaction at the anode
Strike441 [17]

Answer:

a. Minimum 1.70 V

b. There is no maximum.

Explanation:

We can solve this question by remembering that the cell potential is given by the formula

ε⁰ cell = ε⁰ reduction -  ε⁰  oxidation

Now the problem states the cell must provide at least 0.9 V and that the reduction potential of the  oxidized species  0.80 V, thus

ε⁰ reduction -  ε⁰  oxidation ≥  ε⁰ cell

Since ε⁰  oxidation is by definition the negative of ε⁰ reduction , we have

ε⁰ reduction - ( 0.80 V )  ≥  0.90 V

⇒ ε⁰ reduction  ≥ 1.70 V

Therefore,

(a) The minimum standard reduction potential is 1.70 V

(b) There is no maximum standard reduction potential since it is stated in the question that we want to have a cell that provides at leat 0.9 V

8 0
2 years ago
What does the group number on the periodic table tell you about the electron configuration of a
jarptica [38.1K]

Answer:

The group number in the periodic table represents number of valence electrons of the elements in a certain group.

Explanation:

There are s, p, d, and f blocks, which you can see in periodic table

The s-block and p-block together are usually considered main-group elements, the d-block corresponds to the transition metals, and the f-block encompasses nearly all of the lanthanides (like lanthanum) and the actinides (like actinium)

There are three main principles, which may useful for you:

  • The Pauli exclusion rule basically says that at most, 2 electrons are allowed to be in the same orbital.
  • Hund’s rule explains that each orbital in the subshell must be occupied with one single electron first before two electrons can be in the same orbital.
  • The Aufbau process describes the process of adding electron configuration to each individualized element in the periodic table.

Hope this helps!

4 0
3 years ago
When pellets of NaOH(s) are added to a flask of water, it is observed that the temperature of the water increases as the pellets
Nataly [62]

Answer: It is an exothermic process because heat energy is absorbed by the water as the NaOH(s) dissolves in it.

Explanation:

Endothermic reaction : It is a type of chemical reaction where the energy is absorbed from the surrounding. In the endothermic reaction, the reactant are less than the energy of product. In endothermic reaction, the change in enthalpy is, positive

Exothermic reaction : It is a type of chemical reaction where the energy is released into the surrounding. In the exothermic reaction, the energy of reactant are more than the energy of product. In exothermic reaction, the change in enthalpy is, negative.

Thus as energy is absorbed by water, which has been released by NaOH, the process is exothermic.

3 0
3 years ago
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