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SOVA2 [1]
3 years ago
9

How many valence electrons are in an atom of strontium (Sr)? Consult the periodic table. A. 5 B. 2 C. 47.90 D. 22

Chemistry
2 answers:
Eduardwww [97]3 years ago
6 0
<h2>Answer:</h2>

The option B is correct.

Strontium has 2 valence electrons.

<h3>Explanation:</h3>
  • Since strontium (Sr) is in Group 2 it will have 2 valence electrons.
Kaylis [27]3 years ago
5 0

The smallest and the basic particle of a chemical element is said to be an atom. It is made up of three subatomic particles that is electrons, protons and neutrons.  The neutrons and protons are present in the nucleus of an atom whereas electrons are present in the orbits around the nucleus of the atom.  There are several shells in the orbital depending on the atomic number.  The electrons which are present in the outermost shell are said to be valence electrons.

They can be determined by the electronic configuration of the element.

The atomic number of strontium, Sr is 38. The electronic configuration of strontium, Sr is:

1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}

From the electronic configuration it is clear that the outermost shell of strontium, Sr is 5s. So, the number of valence electrons in strontium, Sr is 2.

Hence, there are 2 valence electrons in an atom of strontium (Sr).

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Consider the following thermochemical reaction for kerosene:
ch4aika [34]

We have to solve this question using the stoichiometry of the reaction:

The equation of the reaction is;

2 C12H26(l) + 37 O2(g) -----> 24 CO2(g) + 26 H2O(l) + 15,026 kJ

According to the question;

Number of moles of CO2 released = 21.3 g/44 g/mol = 0.48 moles

From the  stoichiometry of the reaction:

Since;

24 moles of CO2 released 15,026 KJ

0.48 moles of CO2 will release 0.48 * 15,026/24

= 301 KJ of heat.

brainly.com/question/6901180

7 0
3 years ago
Read 2 more answers
Ralph's friend invited him to attend a hard rock concert. Ralph did not want to go because he assumed other people who attended
Iteru [2.4K]

Answer:

Prejudice

Explanation:

8 0
3 years ago
Read 2 more answers
What is the molar out of a solution that contains 33.5g of CaCl2 in 600.0mL of water
omeli [17]

Answer:

Here's what I got.

Explanation:

Interestingly enough, I'm not getting

0.0341% w/v

either. Here's why.

Start by calculating the percent composition of chlorine,

Cl

, in calcium chloride, This will help you calculate the mass of chloride anions,

Cl

−

, present in your sample.

To do that, use the molar mass of calcium chloride, the molar mass of elemental chlorine, and the fact that

1

mole of calcium chloride contains

2

moles of chlorine atoms.

2

×

35.453

g mol

−

1

110.98

g mol

−

1

⋅

100

%

=

63.89% Cl

This means that for every

100 g

of calcium chloride, you get

63.89 g

of chlorine.

As you know, the mass of an ion is approximately equal to the mass of the neutral atom, so you can say that for every

100 g

of calcium chloride, you get

63.89 g

of chloride anions,

Cl

−

.

This implies that your sample contains

0.543

g CaCl

2

⋅

63.89 g Cl

−

100

g CaCl

2

=

0.3469 g Cl

−

Now, in order to find the mass by volume percent concentration of chloride anions in the resulting solution, you must determine the mass of chloride anions present in

100 mL

of this solution.

Since you know that

500 mL

of solution contain

0.3469 g

of chloride anions, you can say that

100 mL

of solution will contain

100

mL solution

⋅

0.3469 g Cl

−

500

mL solution

=

0.06938 g Cl

−

Therefore, you can say that the mass by volume percent concentration of chloride anions will be

% m/v = 0.069% Cl

−

−−−−−−−−−−−−−−−−−−−

I'll leave the answer rounded to two sig figs, but keep in mind that you have one significant figure for the volume of the solution.

.

ALTERNATIVE APPROACH

Alternatively, you can start by calculating the number of moles of calcium chloride present in your sample

0.543

g

⋅

1 mole CaCl

2

110.98

g

=

0.004893 moles CaCl

2

To find the molarity of this solution, calculate the number of moles of calcium chloride present in

1 L

=

10

3

mL

of solution by using the fact that you have

0.004893

moles present in

500 mL

of solution.

10

3

mL solution

⋅

0.004893 moles CaCl

2

500

mL solution

=

0.009786 moles CaCl

2

You can thus say your solution has

[

CaCl

2

]

=

0.009786 mol L

−

1

Since every mole of calcium chloride delivers

2

moles of chloride anions to the solution, you can say that you have

[

Cl

−

]

=

2

⋅

0.009786 mol L

−

1

[

Cl

−

]

=

0.01957 mol L

−

This implies that

100 mL

of this solution will contain

100

mL solution

⋅

0.01957 moles Cl

−

10

3

mL solution

=

0.001957 moles Cl

−

Finally, to convert this to grams, use the molar mass of elemental chlorine

0.001957

moles Cl

−

⋅

35.453 g

1

mole Cl

−

=

0.06938 g Cl

−

Once again, you have

% m/v = 0.069% Cl

−

−−−−−−−−−−−−−−−−−−−

In reference to the explanation you provided, you have

0.341 g L

−

1

=

0.0341 g/100 mL

=

0.0341% m/v

because you have

1 L

=

10

3

mL

.

However, this solution does not contain

0.341 g

of chloride anions in

1 L

. Using

[

Cl

−

]

=

0.01957 mol L

−

1

you have

n

=

c

⋅

V

so

n

=

0.01957 mol

⋅

10

−

3

mL

−

1

⋅

500

mL

n

=

0.009785 moles

This is how many moles of chloride anions you have in

500 mL

of solution. Consequently,

100 mL

of solution will contain

100

mL solution

⋅

0.009785 moles Cl

−

500

mL solution

=

0.001957 moles Cl

−

So once again, you have

0.06938 g

of chloride anions in

100 mL

of solution, the equivalent of

0.069% m/v

.

Explanation:

i think this is it

8 0
2 years ago
Please review the attachment
astra-53 [7]

Answer: The correct answer is -297 kJ.

Explanation:

To solve this problem, we want to modify each of the equations given to get the equation at the bottom of the photo. To do this, we realize that we need SO2 on the right side of the equation (as a product). This lets us know that we must reverse the first equation. This gives us:

2SO3 —> O2 + 2SO2 (196 kJ)

Remember that we take the opposite of the enthalpy change (reverse the sign) when we reverse the equation.

Now, both equations have double the coefficients that we would like (for example, there is 2S in the second equation when we need only S). This means we should multiply each equation (and their enthalpy changes) by 1/2. This gives us:

SO3 —>1/2O2 + SO2 (98 kJ)

S + 3/2O2 —> SO3 (-395 kJ)

Now, we add the two equations together. Notice that the SO3 in the reactants in the first equation and the SO3 in the products of the second equation cancel. Also note that O2 is present on both sides of the equation, so we must subtract 3/2 - 1/2, giving us a net 1O2 on the left side of the equation.

S + O2 —> SO2

Now, we must add the enthalpies together to get our final answer.

-395 kJ + 98 kJ = -297 kJ

Hope this helps!

8 0
3 years ago
Read 2 more answers
A fog over a lake. what two changes of state must occur to produce the fog? do the water molecules absorb or release energy duri
Zolol [24]
The water from the lake must first evaporate from the liquid state to the gaseous state and then condense in the air to form vapors.
The water molecules absorb energy while evaporating and release it when condensing. Their motion gets faster when they are evaporating and slows back down upon condensation.
3 0
3 years ago
Read 2 more answers
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