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just olya [345]
3 years ago
12

Help please Thank You so much!

Chemistry
1 answer:
Irina18 [472]3 years ago
4 0
If you count the number of electrons (small dots), you have the atomic number. In this case you have 11 so this atom is a sodium atom. Sodium has 1 valence electron (electron on the outer shell) and chlorine has 7. This means that if sodium gave one electron away and chlorine would obtain one electron, they would both have the (ideal) noble gas conformation (full outer shell).
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Seismic waves hope this helps.
5 0
3 years ago
12. Which compound can act as both a BrønstedLowry
oksian1 [2.3K]
1) The compound which can act as a <span>Bronsted-Lowry acid and a Bronsted-Lowry base is definitely water - H2O. Remember that water is </span><span>amphoteric which means it can </span>either accept protons or donate them, so it is the most proper option among other represented. Here are examples of both base and acid with water : <span>HCl+H20=H30+Cl ; </span><span>NH3+H2O=NH4+OH 

2) The </span><span>acids in this equilibrium reaction CN– + H2O HCN + OH. Acid species always donate </span> H+ to the species with which they react. In the second option you can see how H2O donates an H+ to CN-. If the reaction gets reversed we will obtain<span> HCN that donates an H+ to OH that shows that it is an acid.
</span><span>
3) </span>The products of self-ionization of water are OH⁻ and H₃O⁺. Self-ionization is an ionization reaction during which  H2O deprotonates its hydrogen atoms to become a hydroxide ion -- OH−. After this process OH-  protonates another water molecule forming H3O+<span>. 

4) The type of </span> solution which is one with a pH of 8 is acidic. Here is a little table that can be a prompt for you if you ever come across such tasks - ph : 7 is neutral<span>. </span>pH<span>  </span>lower than 7<span> are acidic, and </span>pH<span>  higher than </span>7<span> basic ones. 

5) </span><span>The acid dissociation constant for an acid dissolved in water is equal to the equilibrium constant. I consider this option correct because we can obtan </span><span>Kw only when dealing with Kb, and we can conclude that the hydrolysis constant of the conujugate base. 

6) </span>A 0.12 M solution of an acid that ionizes only slightly in solution would be termed dilute and weak. You can determine it depending on its concentration. Such value as 0.12M usually defined as a dilute solution of a weak acid due to the fact that acid represents its <span>partial ionization which is a direct characteristic of a weak acid.
 
7) To solve this task we should appeal to H</span>enry's law that says<span> the solubility of a gaz is proportional to its partial pressure. And according to this we can understand that </span>202kPa is the half of 404kPa which means that the needed solubility must be divided by <span>2 7.5/2=3.75 g/L and that's all.

8) I think that the most important points which best show </span><span>how the addition of a solute affects the boiling point, the freezing
point, and the vapor pressure of the solvent are : BOILING: a</span>dditional attractive forces can only exist between solute and solvent and in order to boil they must be overcome for the solution;we should add KE to overcome the forces. FREEZING : to freeze we have to withdrawn KE as the solute particles are surrounded by solvent molecules. VAPOR : WHen <span>solvent shells are being formed  the solute particles reduces the number of solvent particles that have sufficient KE to vaporize.</span>
<span>
9) </span>[H+][OH-]= Kw = 1.0 * 10^-14
[H+]= Kw/ [OH-]= 1.0x 10^-14 / 1 x 10^-11 =1 x 10^-3 mol/L &#10;&#10;pH = - log [H+]= - log 1 x 10^-3 = 3
Since we got Ph of 3 in a result we can define solution as an acidic one, as I mentioned before.

10) Since the formula of the given acid is HA it undergoes like that :<span> HA<=> H+ + A- .
</span><span>ka = [H][A] / [HA].
Now we have only </span>[H+] and to go further you need to write  <span>electroneutrality equation for the reaction :
</span>[H+] = [OH-] + [A-]  (since [H]>>>[OH]), then 
<span>[H+] = [A-] 
</span>Then mass balance equation : 
Ct = 0.5M = [A-] + [HA] 
<span>[HA] = 0.5 - [A-] = 0.5 - [H+] 
</span>Finally here is what we have done and get : 
ka = [H]^2 / (0.5 - [H+]) &#10;
ka = 0.0001*0.0001/(0.5-0.0001) = 2.00x10^-8

11) The main points that are common for acids : they form Hydrogen ions when dissloved in water, - Ex. Vinegar and Lemon, Ph >7, they have <span>Increased hydrogen ions (H+). The facts about bases : they r</span>educe the concentration of hydgoren ions in a solution which is opposite to asids,<span>- Ex. Antiacid,and Ammonia ,</span>Ph valuse above 7, they form hydrogen (OH-).
- The common points of both acids and bases : <span>Hydrogen ions ,</span>
 both not neutral and water based.
5 0
3 years ago
In a physical change of matter,​
mel-nik [20]

Answer: C. no new substances are formed<span>
</span><span>
<span>In the physical change of matter, there is no new substance that is formed. It is only the appearance of the matter that is being changed and not its chemical composition. Cutting, tearing and grinding are only some of the examples that exhibit physical change. </span></span>

5 0
3 years ago
Read 2 more answers
In the winter , people often buy large bags of rock salt to sprinkle on their walkways . Why do people do this?
slamgirl [31]

The salt causes the water to freeze at a lower temperature. When a solute, aka salt, is introduced to the system, the freezing point is lowered. This makes the water freeze at a lower temperature.

6 0
3 years ago
When limestone (solid ) is heated, it decomposes into lime (solid ) and carbon dioxide gas. This is an extremely useful industri
SVETLANKA909090 [29]

The given question is incomplete, the complete question is:

When limestone (solid CaCO3) is heated, it decomposes into lime (solid CaO) and carbon dioxide gas. This is an extremely useful industrial process of great antiquity, because powdered lime mixed with water is the basis for mortar and concrete — the lime absorbs CO2 from the air and turns back into hard, durable limestone.

Suppose some calcium carbonate is sealed into a limekiln of volume 850 L and heated to 740.0 C. When the amount of CaCO3 has stopped changing, it is found that 2.05 kg have disappeared.

Calculate the pressure equilibrium constant Kp this experiment suggests for the equilibrium between CaCO3 and CaO at 740.0 C. Round your answer to significant digits.

Answer:

The correct answer is 2.00.

Explanation:

Based on the given information, the pressure equilibrium constant or Kp is equivalent to pressure of carbon dioxide or PCO₂. The reaction taking place in the given case is:  

CaCO₃ (s) ⇄ CaO (s) + CO2 (g)

The molecular weight of CO2 is 44 g/mol and the molecular weight of CaCO₃ is 100 g/mol. The amount of CaCO₃ that got disappeared in the given case is 2.05 Kg or 2050 grams. Therefore, the amount of CO₂ is,  

2050 g CaCO₃ * (44 g CO2/100 g CaCO₃) = 902 g CO2

The pressure of CO2, which is equivalent to Kp can be determined by using the formula,  

P = nRT/V

Here V is the volume, which is 850 L, T is the temperature, which is 740 degree C or 1013 K, R is the rate constant, which is 0.0822 L.atm/K.mole

n is the no. of moles, which is equal to weight/molecular wt,  

n = 902 g/44 g/mol = 20.5 mole

Now putting the values we get,  

P = 20.5 mole * 0.0821 L.atm/K.mole * 1013 K / 850 L

P = 2.00 atm or Kp = 2.00

5 0
3 years ago
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