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vekshin1
3 years ago
14

What is the Ka of a weak acid (HA) if the initial concentration of weak acid is 4.5 x 10-4 M and the pH is 6.87? (pick one)

Chemistry
1 answer:
rewona [7]3 years ago
5 0

Answer:

Ka = 4.04 \times 10^{-11}

Explanation:

Initial concentration of weak acid = 4.5 \times 10^{-4}\ M

pH = 6.87

pH = -log[H^+]

[H^+]=10^{-pH}

[H^+]=10^{-6.87}=1.35 \times 10^{-7}\ M

HA dissociated as:

HA \leftrightharpoons H^+ + A^{-}

(0.00045 - x)    x     x

[HA] at equilibrium = (0.00045 - x) M

x = 1.35 \times 10^{-7}\ M

Ka = \frac{[H^+][A^{-}]}{[HA]}

Ka = \frac{(1.35 \times 10^{-7})^2}{0.00045 - 0.000000135}

0.000000135 <<< 0.00045

Therefore, Ka = \frac{(1.35 \times 10^{-7})^2}{0.00045 } = 4.04 \times 10^{-11}

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An unknown compound has a percent composition of 52.10% potassium, 15.8% carbon, and 32.1% oxygen. The molar mass of the compoun
lianna [129]
To determine the empirical formula and the molecular formula of the compound, we assume a basis of the compound of 100 g. We do as follows:

       Mass              Moles                     
K    52.10     52.10/39.10 = 1.33         1.33/1.32 ≈ 1
C    15.8       15.8/12         = 1.32         1.32/1.32 ≈ 1
O     32.1      32.1 / 16       =  2.01        2.01/1.32 ≈ 1.5

The empirical formula would most likely be KCO.
The molecular formula would be K2C2O3.
4 0
3 years ago
Read 2 more answers
Five kilograms of liquid carbon tetrachloride undergo a mechanically reversible, isobaric change of state at 1 bar during which
Drupady [299]

Answer:

Explanation:

From the information given:

Mass of carbon tetrachloride = 5 kg

Pressure = 1 bar

The given density for carbon tetrachloride = 1590 kg/m³

The specific heat of carbon tetrachloride =  0.84 kJ/kg K

From the composition, the initial volume of carbon tetrachloride will be:= \dfrac{5 \ kg }{1590 \ kg/m^3}

= 0.0031 m³

Suppose \beta is independent of temperature while pressure is constant;

Then:

The change in volume can be expressed as:

\int ^{V_2}_{V_1} \dfrac{dV}{V} =\int ^{T_2}_{T_1} \beta dT

In ( \dfrac{V_2}{V_1})  = \beta (T_2-T_1)

V_2 = V_1 \times exp (\beta (T_2-T_1))

V_2 = 0.0031 \ m^3  \times exp  (1.2 \times 10^{-3} \times 20)

V_2 = 0.003175 \ m^3

However; the workdone = -PdV

W = -1.01 \times 10^5 \ Pa \times ( 0.003175 m^3 - 0.0031 \ m^3)

W = - 7.6 J

The heat energy Q = Δ h

Q = mC_p(T_2-T_1)

Q = 5 kg \times 0.84 \ kJ/kg^0 C \times 20

Q = 84 kJ

The internal energy is calculated by using the 1st law of thermodynamics; which can be expressed as;

ΔU = ΔQ + W

ΔU = 84 kJ + ( -7.6 × 10⁻³ kJ)

ΔU = 83.992 kJ

3 0
3 years ago
If 200.0 grams of aluminum chloride react with calcium, how many moles of Al are produced?
irina [24]
1.49 moles of Al will be produced. Hope this helps you.

8 0
3 years ago
I will give BRAINIEst please!!! help meeee omg
Alexxandr [17]

Answer:

(a)57.48 percent (b) 29.45 percent

Explanation:

copper(II) bromide is 29.45 percent copper and 71.54 percent bromine. so the first element percentage composition is always the percentage composition of the compound.

that goes same with sodium hydroxide. it  is 57.48 percent sodium, 40 percent oxygen, and 2.52 percent hydrogen.

4 0
3 years ago
What is the relationship between vapor pressure of a liquid and its boiling point?
Aliun [14]
If the intermolecular forces in a liquid<span> are small, the molecules can easily escape from the surface of the</span>liquid<span>. The </span>liquid<span> will have a high </span>vapour pressure<span>. The normal </span>boiling point<span> is the temperature in which the </span>vapour pressure of a liquid<span> becomes equal to atmospheric </span>pressure<span>.</span>
3 0
3 years ago
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