Final answer:
The pH of a 0.750 M KH₂PO₄ solution cannot be accurately determined without additional information such as the pKa value of the dihydrogen phosphate ion (H₂PO₄₋).
Explanation:
The pH of a solution of 0.750 M KH₂PO₄, potassium dihydrogen phosphate, depends on the acid dissociation constants of phosphoric acid (H₃PO₄), as KH₂PO₄ is its conjugate salt. Typically, to calculate the pH of such a solution, one would use the Henderson-Hasselbalch equation which relates the pH of a buffer solution to the pKa of the acid and the concentrations of the acid and its conjugate base.
However, because there is no other species like phosphoric acid or its other salts present to form a buffer system, and because H₂PO₄₋ (from dissociation of KH₂PO₄) is a weak acid, we may need to approach this problem differently.
Since the direct calculation of pH in this context isn't possible without additional information such as the pKa value of the dihydrogen phosphate ion (H₂PO₄⁻), and because the problem does not ask for assumptions to be made or provide a relevant pKa value, the task cannot be completed.
In practical applications, a pKa value would be required to use the Henderson-Hasselbalch equation, or for the weak acid formula: pH = -log[H⁺] where [H⁺] can be obtained through the equilibrium expression involving the dissociation constant (Ka) and the concentration of H₂PO₄⁻.
The ka value for acetic acid, ch3cooh(aq), is 1.8× 10–5. calculate the ph of a 2.20 m acetic acid solution.
2. In the reaction NO + NO2 ⇌ N2O3, an experiment finds equilibrium concentrations of [NO] = 3.8 M, [NO2] = 3.9 M, and [N2O3] = 1.3 M. What is the equilibrium constant Kc for this reaction?
A. 0.064
B. 0.088
C. 0.114
D. 0.193
Answer:
B. 0.088
Explanation:
I got it right
A sealed beaker of what you are told is aqueous nickel sulfide was given to you by the local chemist and you put it on the window sill. after a few days, you notice that the mixture is getting thick toward the bottom. what is the nature of the initial nickel sulfide mixture, assuming that the temperature on the sill remained approximately constant?
The nature of the initial nickel sulfide mixture : suspension
Further explanationA pure substance can be an element or compound.
The element is a single substance that cannot be broken down anymore or the simplest substance.
While the compound is a pure substance that is formed from a combination of two or more elements through chemical reactions and has a constant chemical ratio.
A mixture is a combination of two or more single substances. The properties of the mixture component are not lost / unchanged as in compounds.
The mixture can be divided into a homogeneous mixture if the composition/ratio of each substance in the mixture is the same and heterogeneous mixture if the ratio of the composition of the substances is not the same (can be varied) in each place.
Mixtures can also be divided into solutions, suspensions, and colloids based mainly on the size of the particles
Homogeneous mixture = Solution
Heterogeneous mixture = suspension, and
The mixture is located between suspension and solution = Colloid
The solution is a mixture of two or more substances consisting of a solute and a solvent. The particle size of the solution is very small, less than 1 nm, it cannot be distinguished between the solute and its solvent medium. Substances in a solution cannot be separated through filtering.
The solution has the same composition in each of its parts.
Suspensions are rough mixes and are heterogeneous. Particle size more than 100 nm.
The mixture is a murky solution, but it gradually separates due to the influence of gravity (undergoes precipitation). Suspension can be separated by filtering.
Colloids are mixtures of dispersed particles and dispersing particles. The size of colloidal particles lies between 1 nm - 100 nm
colloid mixtures cannot be separated through ordinary filtering, but rather with ultrafilters.
Aqueous nickel sulfide (NiS) has been deposited after being placed several days, so it can be classified into a mixture of suspensions
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A heterogeneous mixture
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a homogeneous mixture
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Marie and Calvin dissolved 10 grams of KNO3 in 100 grams of water at 25oC. Next they added 5 grams more. Calvin told Marie that they could continue to add solute until they reached 40 grams because the solution was still
Carbon dioxide gas and liquid water form solid glucose (C6H12O6) and oxygen gas during photosynthesis. Chlorophyll absorbs light in the 600-700 nm region.
a) Write a balanced thermochemical equation for the formation of 1.00 mol of glucose.
... I know that it goes like this: 6CO2(g)+6H2O(l)-->C6H12O6(s)+6O2(g)... this is already balanced but not yet considered a "thermochemical equation"
b) What is the minumum number of photons with Y=680 nm needed to form 1.00 mol of gluscose?
a)
A thermochemical equation is the one which includes heat of the reaction
Heat of reaction is also known as "enthalpy of reaction" ( ΔH rxn) and it is the amount of heat absorbed or evolved during the reaction.
The balanced equation for the reaction can be written as
[tex] 6 CO_{2}(g)+ 6 H_{2}O(l)\rightarrow C_{6}H_{12}O_{6}(s)+ 6O_{2}(g) [/tex]
Let us find ΔH rxn for the given reaction
We need heat of formation of the reactants and products. We will use standard reference table to get this data.
From standard table of enthalpies, we have
[tex] H_{f}^{0} Glucose (s) = -1273.3kJ/mol [/tex]
[tex] H_{f}^{0} CO_{2}(g)= -393.5 kJ/mol [/tex]
[tex] H_{f}^{0} H_{2}O(l)= -285.8 kJ/mol [/tex]
[tex] H_{f}^{0} O_{2}(g)= 0 [/tex]
Enthalpy of reaction can be calculated using following formula
[tex] \bigtriangleup H^{0} _{rxn}= \sum H_{f} (products) - \sum H_{f} ( reactants) [/tex]
Let us plug in the standard enthalpy of formation values we found out from reference table.
[tex] \bigtriangleup H^{0} _{rxn}= [-1273.3 kJ.mol + 0]- [6\times (-393.5kJ/mol) + 6\times (-285.8 kJ/mol)] [/tex]
[tex] \bigtriangleup H^{0} _{rxn}= [-1273.3 kJ.mol]- [-4075.8kJ/mol)] [/tex]
[tex] \bigtriangleup H^{0} _{rxn}= -1273.3 kJ.mol+ 4075.8kJ/mol [/tex]
[tex] \bigtriangleup H^{0} _{rxn}= 2802.5 kJ/mol [/tex]
The thermochemical equation for the given reaction can be written as
[tex] 6 CO_{2}(g)+ 6 H_{2}O(l)\rightarrow C_{6}H_{12}O_{6}(s)+ 6O_{2}(g).....\bigtriangleup H_{rxn} = 2802.5 kJ/mol [/tex]
b)
The wavelength of the light absorbed by chlorophyll is 680 nm.
Let us find the energy of one photon having wavelength = 680 nm.
The relationship between energy and wavelength is given by the following equation.
[tex] E = \frac{h\times c}{\lambda } [/tex]
Where E = energy of the photon
h = Plank's constant = 6.626 x 10⁻³⁴ J.s
c = velocity of light = 3.00 x 10⁸ m/s
λ = wavelength of light = 680 nm.
We need the wavelength in meters.
[tex] 680 nm\times \frac{1 m}{10^{9}nm}= 6.80 \times 10^{-7}m [/tex]
λ = 6.80 x 10⁻⁷ m
Let us find E now.
[tex] E = \frac{6.626\times 10^{-34}J.s\times 3.00 \times 10^{8}m/s}{6.80 \times 10^{-7}m} [/tex]
[tex] E = \frac{1.9878 \times 10^{-25}}{6.80\times 10^{-7}}J [/tex]
[tex] E = 2.92 \times 10^{-19}J [/tex]
Let us convert this to kJ.
[tex] 2.92 \times 10^{-19}J \times \frac{1kJ}{1000 J}= 2.92 \times 10^{-22}kJ [/tex]
Energy of 1 photon = 2.92 x 10⁻²² kJ
The total amount of energy absorbed during the photosynthesis reaction is 2802.5 kJ
Number of photons = Total energy absorbed / Energy of 1 photon
Number of photons = [tex] \frac{2802.5 kJ}{2.92 \times 10^{-22}kJ} [/tex]
Number of photons = 9.60 x 10²⁴
The minimum number of photons needed to form 1.0 mol of glucose is 9.60 x 10²⁴
Of the molecules AlC l 3 and AlB r 3 , which has bonds that are more polar?
AlCl₃ has stronger polar bonds than AlBr₃ due to chlorine's higher electronegativity. The overall polarities of these compounds would also consider their similar trigonal planar structures.
Explanation:Of the molecules AlCl₃ and AlBr₃, AlCl₃ has more polar bonds. Bond polarity arises from the difference in electronegativity between the two atoms forming a bond. Chlorine (Cl) is more electronegative than Bromine (Br), hence, electrons in AlCl₃ are pulled towards Cl more than electrons in AlBr₃ are pulled towards Br. This makes the bonds in AlCl₃ more polar than those in AlBr₃.
In the context of a molecule being polar or nonpolar, apart from just electronegativity, we also need to consider the molecule's geometric structure. However, since both AlCl₃ and AlBr₃ have a similar structure (trigonal planar), influencing factors remain the bond polarities.
The two idealized extremes of chemical bonding: (1) ionic bonding—in which one or more electrons are transferred completely from one atom to another, and the resulting ions are held together by purely electrostatic forces—and (2) covalent bonding, in which electrons are shared equally between two atoms. Most compounds, however, have polar covalent bonds, which means that electrons are shared unequally between the bonded atoms. Figure 3.4.4 compares the electron distribution in a polar covalent bond with those in an ideally covalent and an ideally ionic bond. Recall that a lowercase Greek delta ( δ
) is used to indicate that a bonded atom possesses a partial positive charge, indicated by δ+
, or a partial negative charge, indicated by δ−
, and a bond between two atoms that possess partial charges is a polar bond.
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Which chemical agent will you use to modify the frog heart rate?
Which of the following indicates that an exothermic reaction has occurred? Temperature increases Heat is absorbed Salt is produced Water is formed
Answer: Option (a) is the correct answer.
Explanation:
A chemical reaction where heat energy is absorbed by the reactant molecules is known as an endothermic reaction.For example, [tex]A + B + Heat \rightarrow AB[/tex]
The value of [tex]\Delta H[/tex] = +ve for an endothermic reaction.
In an endothermic reaction, heat being absorbed is utilized to break the bonds. Therefore, temperature of the system decreases.
On the other hand, a chemical reaction in which heat energy is released by the reactant molecules is known as an exothermic reaction. For example, [tex]C + D \rightarrow CD + Heat[/tex] is an exothermic reaction.Generally, there occurs an increase in temperature of the substance or system because of the evolution of heat during an exothermic reaction.
Thus, we can conclude that temperature increases indicates that an exothermic reaction has occurred.
Answer:
Temp increases
Explanation:
A 0.465 g sample of an unknown compound occupies 245 ml at 298 k and 1.22 atm. what is the molar mass of the unknown compound?
a.26.3 g/mol
b.33.9 g/mol
c.12.2 g/mol
d.38.0 g/mol
e.81.8 g/mol
Answer: Option (d) is the correct answer.
Explanation:
It is know that for an ideal gas PV = nRT
where P = pressure
V = volume
n = number of moles = [tex]\frac{mass}{molar mass}[/tex]
R = gas constant = 0.082 [tex]L atm K^{-1} mol^{-1}[/tex]
T = temperature
Therefore, put the given values in the formula above as follows.
PV = nRT
or, PV = [tex]\frac{mass}{molar mass}RT[/tex]
[tex]1.22 atm \times 0.245 L = \frac{0.465 g}{molar mass} \times 0.082 L atm K^{-1} mol^{-1} \times 298 K[/tex]
molar mass = 38.12 g/mol
= 38.0 g/mol (approx)
Therefore, we can conclude that the molar mass of the unknown compound is 38.0 g/mol.
To study Earth’s interior, geologists often rely on indirect methods, such as evidence from fossils. true or false
Answer:
the answer is false, the person that said true is incorect.
Explanation:
Answer: FALSE
Explanation:To study Earth’s interior, geologists often rely on indirect methods, such as evidence from fossils.