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Phoenix [80]
3 years ago
9

You need to produce a buffer solution that has a pH of 4.97. You already have a solution that contains 10. mmol (millimoles) of

acetic acid. How many millimoles of acetate (the conjugate base of acetic acid) will you need to add to this solution?
Chemistry
1 answer:
motikmotik3 years ago
5 0

Answer:

16.9 mmoles are needed to add to the solution

Explanation:

To solve this, we can apply the Henderson Hasselbach equation:

Acetic acid → CH₃COOH

CH₃COOH  +  H₂O  ⇄  CH₃COO⁻   +  H₃O⁺             Ka

That is the acid base equilibrium, to determine the amount:

pKa of acetic acid is 4.74

Henderson Hasselbach formula is:

pH = pKa + log (base/acid)

We replace  →  4.97 = 4.74 + log (B / 10mmoles)

Let's verify mmoles of B

4.97 - 4.74 = log (B/10)

0.23 =  log (B/10)

10^(0.23) = 10^(log (B/10)

1.698 = B/10

B = 1.698 . 10 → 16.9 mmoles

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At an elevated temperature, Kp=4.2 x 10^-9 for the reaction 2HBr (g)---> +H2(g) + Br2 (g). If the initial partial pressures o
Damm [24]

Answer : The partial pressure of H_2 at equilibrium is, 1.0 × 10⁻⁶

Explanation :

The partial pressure of HBr = 1.0\times 10^{-2}atm

The partial pressure of H_2 = 2.0\times 10^{-4}atm

The partial pressure of Br_2 = 2.0\times 10^{-4}atm

K_p=4.2\times 10^{-9}

The balanced equilibrium reaction is,

                                2HBr(g)\rightleftharpoons H_2(g)+Br_2(g)

Initial pressure    1.0×10⁻²       2.0×10⁻⁴      2.0×10⁻⁴

At eqm.            (1.0×10⁻²-2p)   (2.0×10⁻⁴+p)  (2.0×10⁻⁴+p)

The expression of equilibrium constant K_p for the reaction will be:

K_p=\frac{(p_{H_2})(p_{Br_2})}{(p_{HBr})^2}

Now put all the values in this expression, we get :

4.2\times 10^{-9}=\frac{(2.0\times 10^{-4}+p)(2.0\times 10^{-4}+p)}{(1.0\times 10^{-2}-2p)^2}

p=-1.99\times 10^{-4}

The partial pressure of H_2 at equilibrium = (2.0×10⁻⁴+(-1.99×10⁻⁴) )= 1.0 × 10⁻⁶

Therefore, the partial pressure of H_2 at equilibrium is, 1.0 × 10⁻⁶

4 0
4 years ago
What is the mass percent of water in copper (II) sulfate?
Veseljchak [2.6K]
The answer is sulfate pentahydrate 


  Hope this helps you :D
8 0
3 years ago
The mass number of Fe is 56 . how many neutron are there in a single Fe atom
Westkost [7]

Answer:

30 neutrons

Explanation:

Since the mass of the iron nuclide is 56 , there must be 56−26=30 neutrons, 30 massive, neutral particles in this iron nucleus.

8 0
3 years ago
The substance water always has a mass ratio of 11% H to 89% O. If 5.00g of a substance containing H and O was decomposed into .2
Gre4nikov [31]

Answer:

                    No the substance is not water.

Explanation:

                   The balance chemical equation for the decomposition of water is as follow;

                                           2 H₂O = 2 H₂ + O₂

Step 1: <u>Calculate moles of H₂O;</u>

               Moles  =  Mass / M.Mass

               Moles  =  5.0 g / 18.01 g/mol

               Moles  =  0.277 moles of H₂O

Step 2: <u>Calculate Moles of O₂ and H₂ produced by 0.277 moles of H₂O:</u>

According to equation,

                        2 moles of H₂O produced  =  1 mole of O₂

So,

                  0.277 moles of H₂O will produce  =  X moles of O₂

Solving for X,

                     X =  0.277 mol × 1 mol / 2 mol

                     X =  0.138 moles of O₂

Also,

According to equation,

                        2 moles of H₂O produced  =  2 mole of H₂

So,

                  0.277 moles of H₂O will produce  =  X moles of H₂

Solving for X,

                     X =  0.277 mol × 2 mol / 2 mol

                     X =  0.227 moles of H₂

Step 3: <u>Calculate Mass of O₂ and H₂ as;</u>

For O₂:

                 Mass  =  Moles × M.Mass

                 Mass  =  0.138 mol × 31.99 g/mol

                 Mass  =  4.44 g of O₂

For H₂:

                 Mass  =  Moles × M.Mass

                 Mass  =  0.227 mol × 2.01 g/mol

                 Mass  =  0.559 g of H₂

Conclusion:

                   From conclusion it is proved that the amount of H₂ produced by decomposition of 5 g of water should be 0.559 g while in statement it is less i.e. 0.290 g.

6 0
3 years ago
What is the length of the shaded grey area? write your answer to the correct number of significant digits. The unit is cm
alukav5142 [94]

Answer:

1.37cm

Explanation:

It's less than 1.4cm but more than 1.3cm. It's also more than 1.35cm so I guess the best answer would be 1.37cm or round up to 1.4cm

8 0
2 years ago
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