Shawn wants to buy a pair of gloves online. She needs to

The pH of a 0.30 M solution of a weak acid is 2.67. What is the Ka for this acid?

vova2212 [387]

Answer:

Ka → 1.5×10⁻⁵

Option E. None of the above

Explanation:

We propose the reaction of equlibrium

Weak ac.H + H₂O ⇄ Weak ac⁻ + H₃O⁺

Initially we have 0.30 moles of acid in 1 L

In equilibrium we would have:

Weak ac.H + H₂O ⇄ Weak ac⁻ + H₃O⁺

0.30 - x x x

We have the pH, where we can obtanined the x, the [H₃O⁺] in the equilibrium.

pH = - log [H₃O⁺] → [H₃O⁺] = 10^⁻(pH)

[H₃O⁺] = 10⁻²'⁶⁷ = 2.14×10⁻³

So let's determine the concentration of the acid, in the equilibrium

0.30 - 2.14×10⁻³ = 0.29786 → [Weak ac.H]

2.14×10⁻³ → [H₃O⁺] = Conjugate base (Weak ac.⁻)

Let's make the expression for Ka

Ka = [Weak ac.⁻] . [H₃O⁺] / [Weak ac.H]

Ka = x² / 0.30 - x

Ka = (2.14×10⁻³)² / 0.29786 → 1.5×10⁻⁵

6 0

1 year ago

How much heat is required to heat 9.61g of ethanol (CH3CH2OH) from 24.10C to 67.30C?

Licemer1 [7]

Answer:

a.)

To warm the liquid from 35°C to 78°C:

(2.3 J/g-K) x (42.0 g) x (78 - 35) = 4154 J

To vaporize the liquid at 78°C:

(38.56 kJ/mol) x (42.0 g C2H5OH / 46.06867 g C2H5OH/mol) = 35.154 kJ

Total:

4.154 kJ + 35.154 kJ = 39.3 kJ

b.)

To warm the solid from -155°C to -114°C:

(0.97 J/g-K) x (42.0 g) x (-114°C - (-155°C)) = 1670 J

To melt the solid at -114°C:

(5.02 kJ/mol) x (42.0 g C2H5OH / 46.06867 g C2H5OH/mol) = 4.5766 kJ

To warm the liquid from -114°C to 78°C:

(2.3 J/g-K) x (42.0 g) x (78 - (-114)) = 18547 J

To vaporize the liquid at 78°C:

35.154 kJ (as in part a.)

Total:

1.670 kJ + 4.5766 kJ + 18.547 kJ + 35.154 kJ = 59.9 kJ

Explanation:

8 0

2 years ago

The tiara worn by Kate Middleton for her wedding to Prince William of England contains 888 diamonds and belongs to the British m

allsm [11]

Answer:

The number of atoms in the gemstones of that tiara is $8.9125\times 10^{24} atoms$ .

Explanation:

Number of diamonds ion tiara = 888

Mass of each diamond = 1.0 carat = 0.200 g (given)

Mass of 888 diamonds in tiara:

$888\times 0.200 g=177.600 g$

Given that diamond is a form of carbon.

Atomic mass of carbon atom = 12 g/mol

Moles of 77.600 g of carbon = $\frac{177.600 g}{12 g/mol}=14.800 mol$

Number of atoms of carbon 14.800 moles:

$14.800 mol\times 6.022\times 10^{23} atoms =8.9125\times 10^{24} atoms$

The number of atoms in the gemstones of that tiara is $8.9125\times 10^{24} atoms$ .

5 0

2 years ago

A bottle of concentrated aqueous sulfuric acid, labeled 98.0 wt% h2so4, has a concentration of 18.0 m. (a) how many milliliters

nadya68 [22]

n this order, Ď=1.8gmL, cm=0.5, and mole fraction = 0.9 First, let's start with wt%, which is the symbol for weight percent. 98wt% means that for every 100g of solution, 98g represent sulphuric acid, H2SO4. We know that 1dm3=1L, so H2SO4's molarity is C=nV=18.0moles1.0L=18M In order to determine sulphuric acid solution's density, we need to find its mass; H2SO4's molar mass is 98.0gmol, so 18.0moles1Lâ‹…98.0g1mole=1764g1L Since we've determined that we have 1764g of H2SO4 in 1L, we'll use the wt% to determine the mass of the solution 98.0wt%=98g.H2SO4100.0g.solution=1764gmasssolutionâ†’ masssolution=1764gâ‹…100.0g98g=1800g Therefore, 1L of 98wt% H2SO4 solution will have a density of Ď=mV=1800g1.0â‹…103mL=1.8gmL H2SO4's molality, which is defined as the number of moles of solute divided by the mass in kg of the solvent; assuming the solvent is water, this will turn out to be cm=nH2SO4masssolvent=18moles(1800â’1764)â‹…10â’3kg=0.5m Since mole fraction is defined as the number of moles of one substance divided by the total number of moles in the solution, and knowing the water's molar mass is 18gmol, we could determine that 100g.solutionâ‹…98g100gâ‹…1mole98g=1 mole H2SO4 100g.solutionâ‹…(100â’98)g100gâ‹…1mole18g=0.11 moles H2O So, H2SO4's mole fraction is molefractionH2SO4=11+0.11=0.9

5 0

1 year ago

Small quantites of hydrogen gas can be prepared in the laboratory by the addition of aqueous hydrochloric acid to metallic zinc.

ira [324]

Answer: The mass or zinc reacted is 0.624 grams.

Explanation:

We are given:

Total pressure = 1.032 atm

Vapor pressure of water = 32 torr = 0.042 atm (Conversion factor: 1 atm = 760 torr)

To calculate partial pressure of hydrogen gas, we use the equation:

$p_{H_2}=p_T-p_{H_2O}\\\\p_{H_2}=1.032-0.042=0.99atm$