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svp [43]
3 years ago
10

Potassium hydrogen phthalate is often used to standardize solutions of strong bases. Highly pure samples of this solid weak acid

are readily available. It is stable and easy to use in the laboratory. Calculate the molarity of a sodium hydroxide solution if 23.73 mL are required to titrate 0.5816 g of potassium hydrogen phthalate (C8H5O4K).
Chemistry
1 answer:
Mazyrski [523]3 years ago
3 0

Answer:

0.12 M

Explanation:

Molarity of sodium hydroxide = number of moles of sodium hydroxide / volume in liters

equation of reaction between NaOH and Potassium hydrogen phthalate

NaOH(aq) + KHC₈H₄O₄(aq)  KNaC₈H₄O₄(aq) + H₂O(aq)

molar mass of KHC₈H₄O₄ = 204.22g/mol

amount required to titrate with NaOH = 0.5816 g

mole of  KHC₈H₄O₄ = 0.5816 g / 204.22g/mol = 0.00285 mole

considering the equation, 1 mole of NaOH required 1 mole of KHC₈H₄O₄

0.00285 mole  KHC₈H₄O₄ will require 0.00285 mole of NaOH

Molarity = 0.00285 mole  / ( 23.73 ml / 1000ml) L = 0.12 M

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Determine the frequency of radiation whose wavelength is 7.67 x 10^-7 cm. Then, determine the amount of energy in the radiation.
dimulka [17.4K]

Answer:

They frequency = 3.9 * 10^16 Hz

The amount of energy E = 2.58 *10^-17 J

Explanation:

Step 1: Data given

wavelength is 7.67 * 10^-7 cm

Step 2: Calculate the frequency

f = c / λ

⇒ with  λ = the wavelength in nm = 7.67 nm

⇒ with c = the speed of light  = 3.00 * 10^8 m/s

⇒ f = the frequency = TO BE DETERMINED

f = (3.00 * 10^8 m/s) / 7.67 * 10^-9 m

f = 3.9 * 10 ^16 /s = 3.9 * 10^16 Hz

They frequency is 3.9 * 10^16 Hz

Step 3: Calculate the amount of energy

E  =  h *f

⇒ with E = the amount of energy (in joule)

⇒ h = Planck's constant =  6.626  *10^-34 J*s

⇒ with f = the frequency

E =  6.626  *10^-34 J*s * 3.9 * 10^16 Hz

E = 2.58 *10^-17 J

8 0
3 years ago
Acetic acid, CH3CO2H, reacts with ethanol, C2H5OH, to form water and ethyl acetate, CH3CO2C2H5. The equilibrium constant for thi
Irina-Kira [14]

Explanation:

The initial concentrations for a mixture :

Acetic acid at equilibrium = 0.15 M

Ethanol at equilibrium = 0.15 M

Ethyl acetate at equilibrium = 0.40 M

Water at equilibrium = 0.40 M

CH3COOH + C_2H_5OH\rightleftharpoons CH_3CO_2C_2H_5+H_2O

Initially:

0.15 M            0.15 M            0.40 M   0.40 M

At equilibrium

(0.15-x)M       (0.15-x) M     (0.40+x) M   (0.40+x) M

The equilibrium constant is given by expression

K_c=\frac{[CH_3CO_2C_2H_5][H_2O]}{[CH_3COOH][C_2H_5OH]}

4.0=\frac{(0.40-x)\times (0.40-x)}{(0.15+x)\times (0.15+x)}

Solving for x:

x = 0.0333

The equilibrium concentrations for a mixture :

Acetic acid at equilibrium = (0.15-x)M = (0.15-0.033) M = 0.117 M

Ethanol at equilibrium = (0.15-x)M = (0.15-0.033) M = 0.117 M

Ethyl acetate at equilibrium = (0.40+x)M = (0.40+0.033) M = 0.433 M

Water at equilibrium = (0.40+x)M = (0.40+0.033) M = 0.433 M

4 0
3 years ago
Which of the following is most appropriate in measuring the mass of a cow; kilogram, gram or meter? Explain your answer with det
Blababa [14]
The most appropriate unit to take the weight of a cow would be kilograms.

Meters are a unit of distance and are not applicable here
A gram is too small to use in this instance
7 0
3 years ago
Read 2 more answers
An electron confined in a one-dimensional box is observed, at different times, to have energies of 12 eV, 27 eV, and 48 eV. What
Fynjy0 [20]

Answer:

l=3.5*10^{-10}m

Explanation:

From the question we are told that:

1st Energy     E_1=12eV=4(3eV)

2nd Energy  E_2=27eV=9(3eV)

3rd Energy   E_3=48eV=16(3eV)

 

Generally the equation for Energy E for electron in one dimensional box at ground state E_0 is mathematically given by

  E_0=\frac{h}{8ml^2}

  E_0=\frac{h}{8ml^2}

Therefore Length a is mathematically given as

l=\sqrt{\frac{h^2}{8mE_0} }

l=\sqrt{\frac{(6.625*10^{-34})^2}{8(9.1*19^{-31}{(3eV(1.6*10^{-19}))}}

l=3.5*10^{-10}m

8 0
2 years ago
What is the mass in grams of 5.50 mol of sodium?
Zolol [24]

Answer:

126.5g

Explanation:

n=<u>m</u><u> </u>

M

where n is moles

m is mass of substance

M is molar mass

molar mass of sodium is 23g/mol

m=nM

m=5.5(23)

m=126.5

8 0
3 years ago
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