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Sophie [7]
3 years ago
5

Aspirin (acetylsalicylic acid, C9H8O4) is a weak monoprotic acid. To determine its acid-dissociation constant, a student dissolv

ed 2.00 g of aspirin in 0.600 L of water and measured the pH. What was the Ka value calculated by the student if the pH of the solution was 2.61?
Chemistry
1 answer:
BabaBlast [244]3 years ago
8 0

Answer:

The Ka is 3.74 *10^-4

Explanation:

Step 1: Data given

Mass of aspirin = 2.00 grams

Volume of water = 0.600 L

pH of solution = 2.61

Molar mass of acetylsalicylic acid = 180 g/mol

Step 2: The balanced equation

C9H8O4 + H2O ⇆ H3O+ + C9H7O4-

Step 3: Calculate moles acetylsalicylic acid

Moles acetylsalicylic acid = mass / molar mass

Moles acetylsalicylic acid = 2.00 grams / 180 g/mol

Moles acetylsalicylic acid = 0.0111 moles

Step 4: The initial concentration

[C9H8O4] = 0.0111 moles / 0.600 L = 0.0185 M

[H3O+] = 0M

[C9H8O4-] = 0M

Step 5: The concentration at the equilibrium

[C9H8O4] =0.0185 - X M

[H3O+] = XM

[C9H8O4-] = XM

Step 6: Calculate Ka

Ka = [H3O+][C9H7O4-] / [C9H8O4]

Ka = x² / (0.0185 - x)

pH = 2.61;  [H3O+] = 10^-pH = 10^-2.61 = 0.00245 = x

Ka = (0.00245)² / (0.0185 - 0.00245) = 3.74 * 10^-4

The Ka is 3.74 *10^-4

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Answer:

42,3g of H₂O

Explanation:

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62,8 g of NH₃ are:

62,8g×(1mol/17,031g) = <em>3,69 moles of NH₃</em>

62,8 g of O₂ are:

62,8g×(1mol/32g) =<em> 1,96 moles of O₂</em>

For a complete reaction of 1,96 moles of O₂ you need:

1,96mol O₂×(4mol NH₃ / 5molO₂) = 1,57 moles NH₃. As you have 3,69 moles, limiting reactant is O₂.

Assuming a complete reaction, 1,96mol O₂ produce:

1,96mol O₂×(6mol H₂O / 5molO₂) = 2,35 moles of H₂O. In grams:

2,35 moles of H₂O×(18,01g/1mol) = <em>42,3g of H₂O</em>

I hope it helps!

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3 years ago
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How many moles of Fe contains 3.41 x 1023 Fe atoms?
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Lithium nitride reacts with water to produce ammonia and lithium hydroxide according to the equation, Li3N(s) + 3H2O (L) --&gt;
Gemiola [76]

Answer:

0.480 grams

Explanation:

Li₃N(s) + 3D₂O (L) --------------------------> ND₃(g) + 3LiOD (aq)

1             :  3                                            : 1           :  3

Number of moles (n) = Mass in gram/ Molar Mass

Mass of ND₃ = 160 mg

                     = 0.16 g

Molar mass of ND₃=  [14 + (3 x 2.014 )]

                               =    14 + 6.042

                               =  20.042 g/mol

Number of moles of   ND₃  =  0.16/20.042

                                             =  0.007983 moles

From the reaction equation, the mole ratio between   Heavy water (D₂O ) and  ND₃ is  3: 1.

This implies that the number of moles of   Heavy water (D₂O )  required

= 3  x 0.007983 moles

=  0.023949 moles

Molar mass of  Heavy water (D₂O )=  [(2.014 x 2) + 16]

                                                           =  20.028 g/mol

Mass in grams of Heavy water (D₂O )= Number of moles  x Molar mass

                                                            =   0.023949   x  20.028

                                                            =  0.4797 grams

                                                            ≈ 0.480 grams

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Predict the number of each atom needed to form a molecule of potassium Sulfide.
vladimir2022 [97]

Answer:

2.0 atoms of K and 1.0 atom of S are needed to form a molecule of potassium sulfide.

Explanation:

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∴ Every 1.0 molecule of K₂S composed of 2.0 atom of K and 1.0 atoms of S.

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