A buffer is prepared by mixing 204.0 mL of 0.452 M HCl and 0.500 L of 0.400 M sodium acetate (NaC2H3O2):
Calculate the pH of the buffer.
How many grams of KOH must be added to 0.500 L of the buffer to change the pH by 0.15 units?
Answer:
pH = 4.89
0.6171g of KOH must be added
Explanation:
Sodium acetate reacts with HCl producing acetic acid as follows:
NaC2H3O2 + HCl → HC2H3O2 + NaCl
That means the moles added of HCl are moles of acetic acid produced and moles of acetate are initial moles - moles of HCl
Moles HCl = Moles acetic acid:
0.204L * (0.452mol / L) = 0.0822 moles acetic acid.
Initial moles sodium acetate:
0.500L * (0.400mol / L) = 0.200 moles
Moles sodium acetate:
0.200 moles - 0.0822 moles = 0.1172 moles sodium acetate
The pH of this buffer (Mixture of a weak acid and its conjugate base) is obtained using H-H equation:
pH = pKa + log [A-] / [HA]
Where pH is pH of the buffer,
pKa is pKa of the buffer (4.74 for acetic acid)
[A-] Moles of sodium acetate -Conjugate base-
And HA moles of acetic acid -Weak acid-
pH = 4.74 + log [0.1172 moles] [0.0822 moles]
pH = 4.89In 0.500L the moles of the buffer are:
0.500L * (0.200moles / 0.704L) = 0.142 moles of buffer
For a pH of 0.15 units more (4.89 + 0.15 = 5.04):
5.04 = 4.74 + log [Acetate] / [Acetic acid]
0.3 = log [Acetate] / [Acetic acid]
1.9953 = [Acetate] / [Acetic acid] (1)
And as:
0.142 = [Acetate] + [Acetic acid] (2)
Replacing (2) in (1):
1.9953 = 0.142 - [Acetic acid] / [Acetic acid]
1.9953 [Acetic acid] = 0.142 - [Acetic acid]
2.9953 [Acetic acid] = 0.142 moles
[Acetic acid] = 0.0474 moles of acetic acid must remain after the addition of KOH.
In the beginning, moles of acetic acid are:
0.0822 moles * (0.500L / 0.704L) = 0.0584 moles.
That means moles added of KOH (Equal to moles of acetic acid that react) are:
0.0584 moles - 0.0474 moles = 0.0110 moles of KOH
In grams (Molar mass KOH = 56.1g/mol):
0.0110 moles KOH * (56.1g/mol) =
0.6171g of KOH must be added
As you decreased the volume of the chamber, what effect did this change have on the frequency of collisions between
atoms?
Answer: increase number of collisions
Explanation:
Decreasing the volume increases the likelihood of particles interacting more often.
Answer:
Atoms collided more often when the volume was lower.
Explanation:
plato
A sample of 6.44 g of napthalene (C10H8) is dissolved in 80.1 g of benzene (C6H6). Calculate the percent by mass of napthalene in this solution.
Answer:
7.44%
Explanation:
[tex]\frac{6.44}{6.44+80.1} *100=7.44[/tex]
What are two properties that can differentiate between pure nickel and pure
iron?
A. Density and electrical conductivity
B. Magnetism and thermal conductivity
C. Appearance and density
D. Appearance and state at room temperature

Answer: Its "C"
Explanation:
Appearance and density
sorry this took 14 hours lol
pls mark brainiest
You have a two-liter sample of each of the following gases, all at 25 °C and one atmosphere pressure. Which sample will weigh the most?A) Ammonia.B) Argon.C) Carbon dioxide.D) Nitrogen dioxide.E) Oxygen.
Answer: D) Nitrogen Dioxide
Explanation:
The characteristics of moles allow you to find that the correct answer for which sample weighs more is:
D) Nitrogen Dioxide
The molecular weight of the substance is the weight of one mole of a material, where one mole is Avogadro's number of particles.
In all chemical reactions the relationships are given as a function of moles.
Let's find the molecular weight of each of the substances, we take the atomic weights from the periodic table
Element PA (gr / mol)
H 1
C 12
N 14
O 16
Ar 40
A) Ammonia with NH₃ formula
weight of a mole of molecules
MP = 14 + 3
PM = 17 gr / mol
B) Argon symbol Ar
It is a noble gas and does not react
PM = 40 gr / mol
C) Carbon dioxide formula CO₂
Weight per mole of substance
PM = 12 + 2 16
Pm = 44 gr / mol
D) Nitrogen dioxide formula NO₂
Weight per molecular
MP = 14 + 2 16
PM = 46 gr / mol
E) Oxygen symbol O formula O₂
Molecular weights
PM = 2 16
PPM = 32 gr / mol
It indicates that we have two liters of sample, so the number of moles of each substance is the same, therefore the substance that weighs more is Nitrogen Dioxide (NO₂)
When reviewing the different answer, the correct one is:
D) Nitrogen Dioxide
Learn more here: brainly.com/question/19463913
Which of the following elements has the heaviest atom?
a. nickel
b. lead
c. iron
d. gold
Answer:
IronExplanation:
Because it is never because iron weights 9 tons or 17,000 poundsAnswer:
b. lead
Explanation:
look on the periodic table and it has its atomic mass and lead (Pb) is the heaviest
Which of these compounds do not have a pH dependent solubility at less than pH 7.00?
Answer:
tbh idekkk
Explanation:
Why does water have a much higher boiling point than methane even though water (H20) and methane (CH4) molecules are approximately the same size?
A. Only metallic bonds exist between methane molecules.
B. Only Van der Waals forces exist between water molecules.
C. Only metallic bonds exist between water molecules.
D. Only Van der Waals forces exist between methane molecules.
Answer:
Water has a higher boiling point because the hydrogen bonds that form water molecules are stronger than the Van der Waals interactions among methane molecules, therefor more energy must be provided in order to break the hydrogen bonds and allow the water molecules to escape the liquid state.
Explanation:
Water has a much higher boiling point than methane because only Van der Waals forces exist between methane molecules.
What are chemical bonds?Chemical bonds are forces of attraction between ions, molecules, and atoms.
There are different types of bonds present
Covalent bonds are the strongest bonds.
The molecules of water are joined by a hydrogen bond, thus its boiling point is high.
The molecules of Methane are attached by the van der Waals force, and it is weaker than the hydrogen bond.
Thus, methane has a lower boiling point than water.
Weaker bonds easily get broken.
Thus, the correct option is D.
Learn more about Chemical bonds
https://brainly.com/question/6071754
2. If you travel 7.5 km and walk for 1.5 h. what is your average speed
Show Your Work Actual
Answer:
5km/h
Explanation:
Given parameters:
Distance = 7.5km
Time = 1.5h
Unknown:
Average speed = ?
Solution:
Average speed is the distance divided by the time taken.
Average speed = [tex]\frac{total distance }{time taken}[/tex]
Insert the parameters and solve;
Average speed = [tex]\frac{7.5}{1.5}[/tex] = 5km/h
The rate constant for the radioactive decay of tritium 3H is 0.056 1/yr. The percentage of tritium remaining after 50 years is:_________
Answer:
6.05%
Explanation:
From the question given above, the following data were obtained:
Decay constant (K) = 0.0561 /yr
Time (t) = 50 years
We can obtain the percentage of tritium remaining after 50 years by using the following formula:
Log (N₀/N) = kt /2.303
NOTE:
N₀ is the original amount.
N is the amount remaining.
K is the decay constant.
t is the time
Log (N₀/N) = (0.0561 × 50) /2.303
Log (N₀/N) = 2.805/2.303
Log (N₀/N) = 1.218
Take the anti log of 1.218
(N₀/N) = anti log (1.218)
(N₀/N) = 1.218
N₀/N = 16.52
Invert and multiply by 100 to obtain the percentage.
N/N₀ = 1/16.52 × 100
N/N₀ = 6.05%
Thus, the percentage of tritium remaining after 50 years is 6.05%
Answer:
6.08% remains after 50 years
Explanation:
The radioactive decay follows the equation:
Ln[A] = -kt + Ln [A]₀
Where [A] is concentration of reactant after time t, [A]₀ is its initial concentration, k is rate constant and t is time.
Assuming its Initial concentration is 100%
Time is 50 yr
k is 0.056 yr⁻¹
And [A] is our incognite
Ln[A] = -0.056 yr⁻¹*50yr + Ln [100%]
ln[A] = 1.805
[A] =
6.08% remains after 50 years
what are the existing evidences to support the existence of pangea?
salamat.
Fossil evidence for Pangaea includes the presence of similar and identical species on continents that are now great distances apart.
From one run of the proposed electron transport chain, how many ATP equivalents in energy could theoretically be generated?a) 3 b) 4 c) 5 d) 6 e) 7
Answer:
b) 4
Explanation:
The electron transport chain may be defined as the series of the complexes which transfer the electrons from electron donors to the electron acceptors through a redox reactions, and also couples the electron transfer along with the transfer of the protons across the membrane.
The electron transport chain or the ETC is made up of peptides and enzymes, and some other molecules.
The full form of ATP is Adenosine triphosphate. It is a chemical compound that provides energy to the living cells.
From one run in the ETC or the electron transport chain, 4 ATP can be generated.
An atom of an element has two electrons in the first energy level and five electrons in the second energy level. Write the electron configuration and name the element. How many unpaired electrons does an atom of this element have?
Answer:
electronic configuration: 1s^2,2s^2,2p^3
name: nitrogen
unpaired electron: 3
Explanation:
The atom with 2 electrons and 5 electrons in the first and second energy level is NITROGEN. The element has 3 unpaired electron.
The electronic configuration of the atom is 1s² 2s² 2p³Since the atom has 7 Electrons, the element which has 7 electrons is NITROGEN. The 2p orbital has 3 unpaired electrons in it's second energy level.Therefore, the 2p orbital has 3 unpaired electrons in it's outermost shell.
Learn more :https://brainly.com/question/19328396
how many moles of Na2SO4 are in 0.140 m aqueous solution that was prepared with 2.30 kg of water?
Answer:
0.322 mols of NaSO4
Explanation:
Molality = Mols of Solute / kg of Solvent
Molality is given as 0.140 m = mols/kg
kg of solution is given as 2.30 kg
Mols of Solute = Molality * kg of Solvent
Mols of Solute = [tex]\frac{0.140 }{ 1 kg } *2.30 kg[/tex]
Mols of Solute = 0.322 mols
The number of mole of Na₂SO₄ required to prepare the solution is 0.322 mole
The Molality of a solution is defined as the mole of solute per Kg of water i.e
Molality = mole / mass (Kg) of water.
With the above formula, we can obtain the mole of Na₂SO₄ in the solution as follow:
Molality of Na₂SO₄ = 0.140 M
Mass of water = 2.30 Kg
Mole of Na₂SO₄ =.?Mole = Molality × mass of water
Mole of Na₂SO₄ = 0.140 × 2.30
Mole of Na₂SO₄ = 0.322 moleTherefore, the mole of Na₂SO₄ in the solution is 0.322 mole
Learn more: https://brainly.com/question/4251997
Phenol (C6H5OH) is often used as an antiseptic in mouthwashes and throat lozenges. If a mouthwash has a phenol concentration of 1.5 g per 100 mL of solution, what is the molarity of phenol?
Answer:
[tex]M=0.16M[/tex]
Explanation:
Hello!
In this case, since the molarity is defined as moles of solute divided by liters of solution, since we have phenol with a molar mass of 94.12 g/mol, we can first compute the moles in 1.5 g of phenol:
[tex]n=1.5g*\frac{1mol}{94.12 g}=0.016mol[/tex]
Next, since 1000 mL = 1 L, we notice that the volume of the solution is 0.100 L and therefore, the molarity of such solution turns out:
[tex]M=\frac{n}{V}=\frac{0.016mol}{0.100L}\\\\M=0.16M[/tex]
Best regards!
How many different E2 products are expected in the reaction of 3-bromo-1,1-dimethylcyclohexane with NaOCH2CH3?
A) only 1
B) 2
C) 3
D) 4
What is 50% of 36?
O 9
O 16
O 18
O 34
Answer:
18
Explanation:
36 times 0.5
Describe the three kinds of particles found in atoms. Where are they located in the atom and what are their charges?
Dinitrogen tetraoxide, a colorless gas, exists in equilibrium with nitrogen dioxide, a reddish brown gas. One way to represent this equilibrium is:
The question is incomplete, the complete question is shown in the image attached
Answer:
F
T
Explanation:
From the equilibrium equation;
N2O4(g) ⇄NO2(g)
We must have to remember that;
1) At equilibrium, the concentration of the species on both sides of the reaction equation may not necessarily be the same but must be held at a constant value because the rate of forward reaction equals the rate of reverse reaction.
2) The rate of forward reaction must equal the rate of reverse reaction.
If the rate of forward reaction is k1 and the rate of reverse reaction is k2. Then it follows that at equilibrium k1 = k2.
What groups of elements are ionic compounds made of?
Answer:
Ionic compounds generally form between elements that are metals and elements that are nonmetals. For example, the metal calcium (Ca) and the nonmetal chlorine (Cl) form the ionic compound calcium chloride (CaCl2). In this compound, there are two negative chloride ions for each positive calcium ion.
During the formation of water from hydrogen atoms and one oxygen
Answer:
B
Explanation:
hydrogen only has one electron/molecule in it's only shell so it can get together and make a bond
The compound stannous(II) nitride is incorrectly named. Rename the compound correctly.
Answer:
Answer: Tin (II) nitride
An isotope of the element fluorine has 9 protons and 10 neutrons. What is the name of this isotope?
fluorine
Answer:
fluorine atom
Explanation:
A 1.50 mol sample of He occupies a volume of 2.50 L at a pressure of 14.7 atm. What will be the pressure of a 1.50 mol sample of H2 gas under the same conditions? a 7.33atm b 14.7atm c 29.4 atm d 1.00 atm
Answer:
el n = M/m. El nº de moles = m/M
Se utiliza la fórmula general de los gases: P*V = n*R*T
P = 760/760 = 1 atm
V = 0,5 L
n = masa de Cl2/masa molecular = masa de Cl2/70
R = 0,082
T = 273 + 20º C = 293 K
1*0,5 = masa de Cl2/70*0,082*293
0,5/0,082*293 = masa de Cl2/70
0,0208 = masa de Cl2/70
masa de Cl2 = 70*0,0208 = 1,46 g
epilacion:
Suerte
Does MgO have a structure like that of NaCl or ZnS? If the density of MgO is 3.58g/cm3, estimate the radius (in centimeters) of the O2â anions and of the Mg2+ cations.
Answer:
The radius of O^2- is 1.5*10^-8 cm and the radius of
Mg ^2+ is 6.2*10^-9 cm
Explanation:
Face centered cubic : 1/8 atoms on each edges + 1/2 atoms on each face
= [tex]\frac{1}{8}* 8 + \frac{1}{2}*6[/tex] = 4 effective atoms
MgO have a structure like NaCl forms a lattice of FCC.
density of the lattice = [tex]\frac{ z.M}{a^3*Na}[/tex]
z : no of atoms
M: mass of the atoms
a: radius of the atom
Na: Avogadro's number
a^3(radius) = [tex]\frac{ 4*40.3}{3.58*6.022*10^23}[/tex]
a^3 = 7.477 * 10^-23 cm^3
a = 4.21 * 10^-8 cm
Now calculating the anionic(ra O^2-) and cationic (rc Mg^2+)
in Fcc a = 2[tex]\sqrt{2} ra[/tex]
ra = 1.5*10^-8 cm
a = 2ra + 2rc
rc = a/2 -ra
rc = 6.2*10^-9 cm
The radius of O^2- is 1.5*10^-8 cm and the radius of Mg ^2+ is 6.2*10^-9 cm
Of the following, which is NOT a component of the circulatory system?
A. Heart
B. Veins
ws
C. Arteries
D. Brain
Answer:
D. Brain
~PumpkinSpice1
liquid to gas require heat?
Answer:
yes
Explanation:
Answer:
yes
Explanation:
let's say you have ice, you put it on a pan then it heats up you get a liquid after a while it turns into a gas
15.0 moles of gas are in a 8.00 L tank at 22.3 ∘C∘C . Calculate the difference in pressure between methane and an ideal gas under these conditions. The van der Waals constants for methane are a=2.300L2⋅atm/mol2 a=2.300L2⋅atm/mol2 and b=0.0430L/molb=0.0430L/mol.
Answer:
[tex]\Delta P=4.10atm[/tex]
Explanation:
Hello!
In this case, since the ideal gas equation is used under the assumption of no interaction between molecules and perfectly sphere-shaped molecules but the van der Waals equation actually includes those effects, we can compute each pressure as shown below, considering the temperature in kelvins (22.3+273.15=295.45K):
[tex]P^{ideal}=\frac{nRT}{V}=\frac{15.0mol*0.08206\frac{atm*L}{mol*K}*295.45K}{8.00L}=45.5atm[/tex]
Next, since the VdW equation requires the molar volume, we proceed as shown below:
[tex]v=\frac{8.00L}{15.0mol}=0.533\frac{L}{mol}[/tex]
Now, we use its definition:
[tex]P^{VdW}=\frac{RT}{v-b} -\frac{a}{v^2}[/tex]
Thus, by plugging in we obtain:
[tex]P^{VdW}=\frac{0.08206\frac{atm*L}{mol*K}*295.45K}{0.533mol/L-0.0430L/mol} -\frac{2.300L^2*atm/mol^2}{(0.533L/mol)^2}\\\\P^{VdW}=49.44atm-8.09atm\\\\P^{VdW}=41.4atm[/tex]
Thus, the pressure difference is:
[tex]\Delta P=45.5atm-41.4atm\\\\\Delta P=4.10atm[/tex]
Best regards!
PLEASE HELP!!!!
what happens when the ocean reaches it’s saturation level of carbon dioxide?
Hi!
When the ocean reaches its saturation level of carbon dioxide, a couple of things will happen:
First, more carbon dioxide will remain in the atmosphere, and second, the ocean's pH will drop.
Carbonate and bicarbonate ions in seawater act as a buffer system which keeps the ocean's pH levels stable. When CO2 dissolves in seawater, it reacts with the ocean's buffer system in such a way that it produces two hydrogen ions, which lowers the pH. As more and more CO2 reacts with the ocean's buffer system and the system becomes saturated, less atmospheric carbon dioxide will cross over into the ocean. This excess CO2 will remain in the atmosphere and contribute to global climate change.
Hope this helped!
When the ocean reaches it's saturation level of carbon dioxide more amount of carbon dioxide remains in the atmosphere and pH of the ocean drops.
What is saturation level?It is defined as the level or extent up-to which a substance is soluble in a particular solvent. Due to global warming ,there is an excessive release of carbon dioxide in atmosphere. The excessive amount cannot be soluble in the ocean water which leads to ocean acidification.
As a result of ocean acidification the pH of water in the ocean drops thus there is less amount of oxygen present for aquatic organisms which is needed to survive. When carbon dioxide dissolves in water it yields carbonic acid which further reduces the pH of water and thus making it unfit for aquatic environment.
Learn more about saturation level,here:
https://brainly.com/question/13781023
#SPJ2
amu.
An atom with 4 protons, 5 neutrons, and 4 electrons has an atomic mass of
(Enter a whole number.)
Answer:
Explanation:
the sum of number of proton and neutron is known as atomic mass
so if number of proton is 4 and neutron is 5 then atomic mass of an atom is 9