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Dvinal [7]
3 years ago
5

How many grams of sodium benzoate, C H CO Na, have to be added to 1.50 L of a 0.0200 M solution of benzoic acid, C H CO H, to ma

ke a buffer with a pH = 4.00, assuming no volume change?
Chemistry
1 answer:
Dmitrij [34]3 years ago
4 0

Answer: 2.8275grams

Explanation: A buffer is made btw a weak acid and it salt. In a solution made by dissolving a weak acid in solution, equilibrium is set up btw ionised and unionised ion. For Benzoic acid

C6H5COOH....> C6H5COO- + H+

Ka = [C6H5COO-] [H+]/ [C6H5COOH].......(1)

using Ka = 6.5× 10^-5, [C6H5COOH] = 0.02M. PH= - log[H+] ....> [H+]= 10^-4M.

Putting the values in(1)

[C6H5COO-]= 6.5× 10^-5 × 0.02/ 10^-4

[C6H5COO-] = 0.013M = Molarity of sodium benzoate

Mole(C6H5COONa) = 0.013 × Volume = 0.013mol/litre × 1.5 litre

Mole(C6H5COONa) = 0.0195mol

Mass(C6H5COONa) = 0.0195 × Molar mass

Mass(C6H5COONa) = 2.8275g

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Ammonia can be produced in the laboratory by heating ammonium chloride
AnnyKZ [126]

Answer:

Mass = 2.89 g

Explanation:

Given data:

Mass of NH₄Cl = 8.939 g

Mass of Ca(OH)₂ = 7.48 g

Mass of ammonia produced = ?

Solution:

2NH₄Cl   +  Ca(OH)₂     →    CaCl₂ + 2NH₃ + 2H₂O

Number of moles of NH₄Cl:

Number of moles = mass/molar mass

Number of moles = 8.939 g / 53.5 g/mol

Number of moles = 0.17 mol

Number of moles of Ca(OH)₂ :

Number of moles = mass/molar mass

Number of moles = 7.48 g / 74.1 g/mol

Number of moles = 0.10 mol

Now we will compare the moles of ammonia with both reactant.

                      NH₄Cl          :          NH₃

                          2              :           2

                         0.17          :          0.17

                   Ca(OH)₂         :          NH₃

                        1                :           2

                    0.10              :          2/1×0.10 = 0.2 mol

Less number of moles of ammonia are produced by ammonium chloride it will act as limiting reactant.

Mass of ammonia:

Mass = number of moles × molar mass

Mass = 0.17 mol × 17 g/mol

Mass = 2.89 g

6 0
2 years ago
Omar wrote a hypothesis about batteries called dry cells.
Flura [38]
Below are the choices:

<span>The independent variable is the number of dry cells, and the dependent variable is the length of time the bulb works.
</span><span>The independent variable is the length of time the bulb works, and the dependent variable is the number of dry cells.
</span><span>The independent variable is the number of dry cells, and the dependent variable is the amount of energy available.
</span><span>The independent variable is the amount of energy available, and the dependent variable is the number of dry cells.
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I think the answer is <span>The independent variable is the number of dry cells, and the dependent variable is the amount of energy available.</span>
6 0
3 years ago
Read 2 more answers
I have no idea what to do please help me quickly!
Irina18 [472]

Answer:

The farther away the planet the slower the revolution around the earth. the closer the faster.

Explanation:

its like a tetherball pole when it wraps around it gets closer and spins faster and faster untill it stops. Brainliest?

6 0
3 years ago
Read 2 more answers
Please help me I will really appreciate it !!!! And Please no links
BigorU [14]

Explanation:

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3 0
2 years ago
How much energy is needed to warm 7.40g of water by 55 degress C?
zloy xaker [14]
<span>E = mCdT
E = energy, m = mass, C = specific heat capacity, dT = change in temperature.
526 = 0.074C x 17
E = 0.074C x 55
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E/526 = (0.074C x 55)/(0.074C x 17) = 55/17
E = (55 x 526)/17 = 1702 J</span>
8 0
3 years ago
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