5 Which two elements are combined in magnesium oxide?

How can you experimentally determine the pK_a of acetic acid? Determine the pH of the solution 1/4 of the way to the end-point o

Vlad1618 [11]

Answer:

Determine the pH of the solution half-way to the end-point on the pH titration curve for acetic acid.

Explanation:

The equation for the ionization of acetic acid is

HA + H₂O ⇌ H₃O⁺ + A⁻

For points between the starting and equivalence points, the pH is given by the Henderson-Hasselbalch equation:

$\text{pH} = \text{pK}_{\text{a}} + \log\dfrac{[\text{A}^{-}]}{\text{[HA]}}$

At the half-way point, half of the HA has been converted to A⁻, so [HA] = [A⁻]. Then,

$\text{pH} = \text{pK}_{\text{a}} + \log\dfrac{1}{1} = \text{pK}_{\text{a}} + 0 \\\\\text{pH} = \text{pK}_{\text{a}}$

The pKₐ is the pH at the half-way point in the titration.

8 0

3 years ago

How much heat is absorbed by a 112.5 g sample of water when it is heated from 12.5 °C to 9°C? (Specific heat capacity of water i

Oduvanchick [21]

Answer:

–1647.45 J

Explanation:

From the question given above, the following data were obtained:

Mass (M) = 112.5 g

Initial temperature (T₁) = 12.5 °C

Final temperature (T₂) = 9°C

Specific heat capacity (C) = 4.184 J/g°C

Heat (Q) absorbed =?

Next, we shall determine the change in temperature. This can be obtained as follow:

Initial temperature (T₁) = 12.5 °C

Final temperature (T₂) = 9°C

Change in temperature (ΔT) =?

ΔT = T₂ – T₁

ΔT = 9 – 12.5

ΔT = –3.5 °C

Finally, we shall determine the heat absorbed. This can be obtained as follow:

Mass (M) = 112.5 g

Change in temperature (ΔT) = –3.5 °C

Specific heat capacity (C) = 4.184 J/g°C

Heat (Q) absorbed =?

Q = MCΔT

Q = 112.5 × 4.184 × –3.5

Q = –1647.45 J

5 0

3 years ago

If a neutral atom has 10 proton how many electrons would it have?

olchik [2.2K]

It should have 10 electrons

7 0

3 years ago

Read 2 more answers

What is the relationship between the following compounds??

34kurt

And what are the compounds?

8 0

4 years ago

Many power plants produce energy by burning carbon-based fuels, which also produces carbon dioxide. Carbon dioxide is a greenhou

RUDIKE [14]

Answer:

a) 2.541 mol/MJ;

b) 1.124 mol/MJ;

c) 0.4354 mol/MJ;

d) 0.1835 mol/MJ

Explanation:

The enthalpy of formation (ΔH°f) is the enthalpy of a reaction to form a compound by its constituents. For CO₂, ΔH°f = - 393.5 kJ/mol.

The enthalpy of a reaction is the sum of the enthalpy of the products (each one multiplied by the number of moles) less the sum of the enthalpy of the reactants (each one multiplied by the number of moles). The ΔH°f for simple substances (with one atom) is 0. The combustion is the reaction between the fuel and the oxygen.

a) The combution reaction is:

C(s) + O₂(g) → CO₂(g)

ΔH°rxn = -393.5 kJ/mol = -393.5x10⁻³ MJ/mol

Number of moles per MJ released: 1/|ΔH°rxn|

n = 1/(393.5x10⁻³) = 2.541 mol/MJ

b) The combustion reaction is:

CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l)

H₂O is in the liquid state because it's at 1 atm and 25ºC.

ΔH°f, H₂O(l) = -285.3 kJ/mol

ΔH°f, O₂(g) = 0

ΔH°f, CH₄(g) = -74.8 kJ/mol

ΔH°rxn = [2*(-285.3 ) + 1*(-393.5)] - [1*(-74.8)]

ΔH°rxn = -889.3 kJ/mol = -889.3x10⁻³ MJ/mol

n = 1/889.3x10⁻³ = 1.124 mol/MJ

c) C₃H₈(g) + 10O₂(g) → 3CO₂(g) + 4H₂O(l)

ΔH°f,C₃H₈(g) = -25.2 kJ/mol

ΔH°rxn = [4*(-285.3) + 3*(-393.5)] - [1*(-25.2)]

ΔH°rxn = -2,296.5 kJ/mol = -2.2965 MJ/mol

n = 1/2.2965 = 0.4354 mol/MJ

d) C₈H₁₈(l) + (25/2)O₂(g) → 8CO₂(g) + 9H₂O(l)

ΔH°f, C₈H₁₈(l) = -250.1 kJ/mol

ΔH°rxn = [9*(-283.5) + 8*(-393.5)] - [1*(-250.1)]

ΔH°rxn = -5,449.4 kJ/mol = -5.4494 MJ/mol

n = 1/5.4494 = 0.1835 mol/MJ

4 0

3 years ago