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3 years ago

Determine the mass of sodium acetate necessary to produce 100 ml of an acetate buffer

Chemistry

1 answer:

sasho [114]3 years ago

3 0

Explanation:

Ethanoic acid is a weak acid and dissociates:

⇌

−

For which

[

−

]

[

]

[

]

1.8

−

Please remember that these are equilibrium concentrations .

−

log

−

log

[

1.8

−

]

4.74

∴

0.20

200.0

1000

0.04

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motikmotik

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3 years ago

What is the molarity of the Ca(OH)2 solution if 32.00 mL of Ca(OH)2 requires 16.08 mL of a 2.303 M solution for complete titrati

amm1812

Answer:

For this problem we just need to remember the equation and that the volume is always in liters: MaVa=MbVb

Ma= 1.338 mol/L Va= 18.75 mL= 0.01875 L Mb= x Vb=24.73 mL= 0.02473 L

So now we can plug into the equation and solve:

1.338 mol/L * 0.01875 L= x mol/L * 0.02473 L

This is a two step process: stoichiometry and using the answer from the first part to plug and chug it into the Molariy equation.

First step: setup the stoichiometry problem:

3.1171 g Na2CO3 * (1 mol/106 g) * (2 mol HCl/ 1 mol Na2CO3)= mol HCl

Second step: Molarity equation

Molarity= moles HCl/ L M= mol HCl/0.04027 L

For the third problem, you will just use the same equation as the first: MaVa= MbVb

Ma=0.57 M Va= x L Mb= 0.875 M Vb= 23.83 mL= 0.02383 L

0.57 M * x L= 0.875 M * 0.02383 L

With this equation, we want to find the moles of NaOH by using the molarity equation first then because MaVa= MbVb, we know that the number of moles has to be equal.

0.75 M= x mol/ 0.0227 L mol NaOH = 0.75 M *0.0227 L mol NaOH= 0.017025

So next, we can set it to the mass of the acid using this equation: Molar Mass= mass/ moles

Molar Mass= 3.6 g/ 0.017025 mol

And with that you will find the molar mass of HX, and even determine what X is.

Explanation:

hope I helped

8 0

3 years ago

Arrange the following H atom electron transitions in order of increasing frequency of the photon absorbed or emitted:

Temka [501]

The question is incomplete , complete question is:

Arrange the following H atom electron transitions in order of increasing frequency of the photon absorbed or emitted:

(a) n = 2 to n = 4

(b) n = 2 to n = 1

(d) n = 4 to n = 3

Answer:

Hence the order of the transition will be : d < a < c < b

Explanation:

$E_n=-13.6\times \frac{Z^2}{n^2}ev$

where,

$E_n$ = energy of $n^{th}$ orbit

n = number of orbit

Z = atomic number

Energy of n = 1 in an hydrogen atom:

$E_1=-13.6\times \frac{1^2}{1^2}eV=-13.6 eV$

Energy of n = 2 in an hydrogen atom:

$E_2=-13.6\times \frac{1^2}{2^2}eV=-3.40eV$

Energy of n = 3 in an hydrogen atom:

$E_3=-13.6\times \frac{1^2}{3^2}eV=-1.51eV$

Energy of n = 4 in an hydrogen atom:

$E_4=-13.6\times \frac{1^2}{4^2}eV=-0.85 eV$

Energy of n = 5 in an hydrogen atom:

$E_5=-13.6\times \frac{1^2}{5^2}eV=-0.544 eV$

a) n = 2 to n = 4 (absorption)

$\Delta E_1= E_4-E_2=-0.85eV-(-3.40eV)=2.55 eV$

b) n = 2 to n = 1 (emission)

$\Delta E_2= E_1-E_2=-13.6 eV-(-3.40eV)=-10.2 eV$

Negative sign indicates that emission will take place.

c) n = 2 to n = 5 (absorption)

$\Delta E_3= E_5-E_2=-0.544 eV-(-3.40eV)=2.856 eV$

d) n = 4 to n = 3 (emission)

$\Delta E_4= E_3-E_4=-1.51 eV-(-0.85 eV)=-0.66 eV$

Negative sign indicates that emission will take place.

According to Planck's equation, higher the frequency of the wave higher will be the energy:

$E=h\nu$

h = Planck's constant

$\nu$ frequency of the wave

So, the increasing order of magnitude of the energy difference :

$E_4$

And so will be the increasing order of the frequency of the of the photon absorbed or emitted. Hence the order of the transition will be :

: d < a < c < b

7 0

4 years ago

A catalyst can increase the rate of a reaction ________. Select one: a. by increasing the overall activation energy (Ea) of the

makvit [3.9K]

Answer:

by providing an alternative pathway with a lower activation energy

Explanation:

Cataysts are the substances that neither consumed nor produced during a chemical reaction, but increase the rate of the reaction.

So, catalysts remain chemically unchnaged after the completion of the reaction.

For a reaction to occur, reactants molecule must collide and successful collisions lead to product formation.

A certain minimum amount of energy is required for successful collision. This minimum amounr of energy is called activation energy.

One way to increase speed of reaction is to provide energy to the reactants and other way to increase speed is to provide alternate pathway with lower activation energy.

Catalyst increases a rate of reaction by providing an alternate pathway with lower activation energy.

Therefore, the correct option is option b 'by providing an alternative pathway with a lower activation energy'

5 0

4 years ago

How many Sr2+ ions are in a mole of Sr3(PO4)2 ?

jeka94

Each molecule of Sr₃(PO₄)₂ contains 3 moles of Sr
So 3 moles of Sr⁺² ions are in one mole of Sr₃(PO₄)₂.

7 0

3 years ago