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Lilit [14]
2 years ago
6

Which electron configuration represents a selenium atom in an excited state?(1) 2-7-18-6(2) 2-7-18-7(3) 2-8-18-6(4) 2-8-18-7

Chemistry
1 answer:
rosijanka [135]2 years ago
5 0
(2) 2 - 7 - 18 - 7 does, because the electron from the L shell jumped to the N shell, which requires energy.

The rest of them are either different types of atoms (different elements) or are not the excited state (ground state)
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A 5.00 gram sample of an oxide of lead PbxOy contains 4.33g of lead. Determine the simplest formula for the compound.
Valentin [98]
PbO2

You have to take the mass of lead in the problem, and divide by the molar mass.
When you do the same with oxygen, you get a number about twice as large as when you divide the mass of lead by the molar mass of lead. This means that the simplest formula  would be PbO2

8 0
3 years ago
Why does ice have a different density than liquid water?
gulaghasi [49]

Answer:

because it has lighter molecules.

4 0
3 years ago
A chemistry student needs of acetic acid for an experiment. He has available of a w/w solution of acetic acid in acetone. Calcul
Volgvan

Answer:

49.4 g Solution

Explanation:

There is some info missing. I think this is the original question.

<em>A chemistry student needs 20.0g of acetic acid for an experiment. He has 400.g  available of a 40.5 %  w/w solution of acetic acid in acetone.  </em>

<em> Calculate the mass of solution the student should use. If there's not enough solution, press the "No solution" button. Round your answer to 3 significant digits.</em>

<em />

We have 400 g of solution and there are 40.5 g of solute (acetic acid) per 100 grams of solution. We can use this info to find the mass of acetic acid in the solution.

400gSolution \times \frac{40.5gSolute}{100gSolution} = 162 g Solute

Since we only need 20.0 g of acetic acid, there is enough of it in the solution. The mass of solution that contains 20.0 g of solute is:

20.0gSolute \times \frac{100gSolution}{40.5gSolute} = 49.4g Solution

4 0
2 years ago
In reaction CFCl3 + UV Light -&gt; CFCl2 + Cl, there is only one reactant (CFCl3) and no collision
Alla [95]

The reaction CFCl3 + UV Light -> CFCl2 + Cl does not need another reactant as with CFCl3 because the reaction itself is reactive to light. Note that there are reactions that are sensitive to light to form products and when this type of reaction are not exposed to light, no reaction occurs. 
3 0
3 years ago
A metal sample weighing 129.00 grams and at a temperature of 97.8 degrees Celsius was placed in 45.00 grams of water in a calori
Nitella [24]

Answer : The specific heat of metal is 0.481J/g^oC.

Explanation :

In this problem we assumed that heat given by the hot body is equal to the heat taken by the cold body.

q_1=-q_2

m_1\times c_1\times (T_f-T_1)=-m_2\times c_2\times (T_f-T_2)

where,

c_1 = specific heat of metal = ?

c_2 = specific heat of water = 4.184J/g^oC

m_1 = mass of metal = 129.00 g

m_2 = mass of water = 45.00 g

T_f = final temperature = 39.6^oC

T_1 = initial temperature of metal = 97.8^oC

T_2 = initial temperature of water = 20.4^oC

Now put all the given values in the above formula, we get

129.00g\times c_1\times (39.6-97.8)^oC=-45.00g\times 4.184J/g^oC\times (39.6-20.4)^oC

c_1=0.481J/g^oC

Therefore, the specific heat of metal is 0.481J/g^oC.

4 0
3 years ago
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