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MrMuchimi
2 years ago
6

Consider the following weak acids and their Ka values: Acetic Acid Ka = 1.8×10^−5 Phosphoric Acid Ka = 7.5×10^−3 Hypochlorous Ac

id Ka = 3.5×10^−8. What weak acid-conjugate base buffer system from the acids listed is the best choice to prepare the following buffers. Explain your reasoning.
a. pH 2.8
b. pH 4.5
c. pH7.5
Chemistry
1 answer:
vfiekz [6]2 years ago
7 0

Answer:

a. Phosphoric Acid

b. Acetic Acid

c. Hypochlorous Acid

Explanation:

A buffer works when the pH of this one is in pKa ± 1. That means, to find which buffer system works in some pH you need to find pKa:

pKa = -log Ka

<em>pKa Acetic acid:</em>

-log1.8x10⁻⁵ = 4.74

<em>pKa phosphoric acid:</em>

-log7.5x10⁻³ = 2.12

<em>pKa hypochlorous acid:</em>

-log3.5x10⁻⁸ = 7.46

a. For a pH of 2.8 the best choice is phophoric acid because its effective range is: 1.12 - 3.12 and 2.8 is between these values.

b. pH 4.5. Acetic acid. effective between pH's 3.74 - 5.74

c. pH 7.5. Hypochlorous acid that works between 6.46 and 8.46

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Nitella [24]

Answer:

Number of moles = 2.89 mol

Explanation:

Given data:

Number of moles of sugar  = ?

Mass of sugar = 990 g

Solution:

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Number of moles = mass/molar mass

Molar mass of C₁₂H₂₂O₁₁:

12× 12 + 22×1.008 + 16×11 = 342.2 g/mol

Number of moles = 990 g / 342.2 g/mol

Number of moles = 2.89 mol

6 0
3 years ago
5 The apparatus shown below was set up. Give explanations for the following observations.
lana [24]

Answer:

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Explanation:

3 0
2 years ago
X-rays had a frequency of about 3x10^18 determine it's wavelength (in nm) and energy per photon
Serggg [28]

Answer:

E = 19.89×10⁻¹⁶ J

λ = 1×10⁻¹ nm

Explanation:

Given data:

Frequency of xray = 3×10¹⁸ Hz

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Energy of xray = ?

Solution:

speed of wave = wavelength × frequency

speed = 3×10⁸ m/s

3×10⁸ m/s  = λ ×3×10¹⁸ s⁻¹

λ = 3×10⁸ m/s  / 3×10¹⁸ s⁻¹

λ = 1×10⁻¹⁰m

m to nm:

λ = 1×10⁻¹⁰m×10⁹

λ = 1×10⁻¹ nm

Energy of x-ray:

E = h.f

h = plancks constant = 6.63×10⁻³⁴ Js

by putting values,

E = 6.63×10⁻³⁴ Js ×3×10¹⁸ s⁻ ¹

E = 19.89×10⁻¹⁶ J

7 0
2 years ago
an element has atomic number and mass number 13 and 27 respectively. what are the number of electrons protons and neutrons in on
vfiekz [6]

Answer:

the number of electrons is 13 and neutrons is 14

3 0
3 years ago
Traumatic acid contains 63.13% carbon, 8.830% hydrogen, and 28.03% oxygen. its molar mass is 228 g/mol. determine the empirical
Zina [86]
Q1)
firstly we need to determine the empirical formula of the compound. empirical formula is the simplest ratio of components in the compound.
percentages of the elements have been given, so lets assume we are calculating for a compound of 100g 
                                  C                               H                              O
mass                       63.13 g                    8.830 g                       28.03 g
molar mass             12 g/mol                   1 g/mol                      16 g/mol
number of moles     63.13/12                   8.830/1                      28.03/16
                                5.26                           8.830                           1.75
divide by the smallest number of moles 
                                5.26/1.75                   8.830/1.75                   1.75/1.75
                                = 3.01                        = 5.04                           =1
rounded off to the nearest whole numbers 
C - 3
H - 5
O - 1
therefore empirical formula = C₃H₅O

Q2)
we have to next determine the molecular formula of the compound 
molecular formula gives the actual composition of elements in the compound. 
since we know the empirical formula and molecular mass, we can find how many empirical units are in the molecular formula.
mass of empirical unit = Cx3 + Hx5 + Ox1
                                    = 12 g/mol x 3 + 1g/mol x 5 + 16 g/mol x 1
                                    = 36 + 5 + 16 = 57 g/mol
the molecular mass = 228 g/mol
then number of empirical units in the molecular formula = 228 / 57 = 4
therefore there are 4 empirical units 
then the molecular formula = 4 x empirical formula =4 (C₃H₅O)
molecular formula = C₁₂H₂₀O₄




3 0
3 years ago
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