What is cement used for
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a. What is the pKa of X-281? Express your answer numerically.
At 25∘C, for any conjugate acid-base pair
pKa + pKb = 14.00
b. What is pKb of the conjugate base of X-281? (Assume 25 ∘C.) Express your answer numerically.
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Answer:
a. pka = 3,73.
b. pkb = 10,27.
Explanation:
a. Supposing the chemical formula of X-281 is HX, the dissociation in water is:
HX + H₂O ⇄ H₃O⁺ + X⁻
Where ka is defined as:
In equilibrium, molar concentrations are:
[HX] = 0,089M - x
[H₃O⁺] = x
[X⁻] = x
pH is defined as -log[H₃O⁺]], thus, [H₃O⁺] is:
[H₃O⁺] = 0,004M
Thus:
[X⁻] = 0,004M
And:
[HX] = 0,089M - 0,004M = 0,085M
ka = 1,88x10⁻⁴
And pka = 3,73
b. As pka + pkb = 14,00
pkb = 14,00 - 3,73
pkb = 10,27
I hope it helps!
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Answer: the mass of an electron is approximately 9.10938356 × 10^-31 kilograms (kg)
Explanation:
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Oxide ions have a 2+ charge: This is false, oxide ions have a 2- charge.
Electrons do have a negative charge, this is true.
Hydrogen molecule: pretty sure this is true. We know this because both atoms are non-metals.
The last one is true: a covalent bond is a shared pair of electrons between two atoms, however be aware that there can be more than one covalent bond between two molecules.
Answer:
- False , shared electrons cause covalent bonds
- False , they have 2- charge
- True
- True
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Step 1:
Epoxidation of Alkene:
In first step Cyclohexene is treated with peroxybenzoic acid in the presence of Dichloromethane which results in the formation of epoxide moiety.
Step 2:
Nucleophillic Substitution Reaction:
In second step the epoxide formed is treated with Sodium Methoxide which acts as a nucleophile and attacks the less hindered carbon of epoxide resulting in the formation of final product as shown below.
Final answer:
The best reagent and condition for a chemical reaction is dictated by the reactants at hand and the substance that you're trying to produce. For instance, to convert an alkene into an alcohol, Osmium Tetroxide (OsO4) at room temperature would be an example of an ideal reagent and condition.
Explanation:
In chemistry, when you are asked to place the best reagent and conditions in a reaction box, you are trying to predict the proper chemical, heat, or pressure conditions that will foster a certain chemical reaction. This requires understanding of substances' chemical properties, behavior under different conditions, and reaction mechanisms. For instance, if we want to oxidize an alkene into an alcohol, we would choose a reagent like Osmium Tetroxide (OsO4). In this case, OsO4 would be our 'best reagent', and room temperature may serve as the ideal condition as it generally facilitates this process. Each reagent and condition depend on the reactants you start with and the product you want at the end.
Learn more about Chemical Reactions here:
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Answer:
Geologists agree that Devils Tower began as magma, or molten rock buried beneath the Earth’s surface. What they cannot agree upon are the processes by which the magma cooled to form the Tower, or its relationship to the surrounding geology of the area. Numerous theories have been suggested to explain how Devils Tower formed. Geologists Carpenter and Russell studied Devils Tower in the late 1800s and concluded that the Tower was formed by an igneous intrusion (the forcible entry of magma through other rock layers). Later geologists searched for more detailed explanations.
The simplest explanation is that Devils Tower is a stock—a small intrusive body formed by magma which cooled underground and was later exposed by erosion (Figure 1). In 1907, scientists Darton and O’Hara decided that Devils Tower must be an eroded remnant of a laccolith. A laccolith is a large, mushroom-shaped mass of igneous rock which intrudes between the layers of sedimentary rocks but does not reach the surface. This produces a rounded bulge in the sedimentary layers above the intrusion (Figure 2). This idea was quite popular in the early 1900s when numerous studies were done on a number of laccoliths in the American southwest.
Other ideas have suggested that Devils Tower is a volcanic plug or that it is the neck of an extinct volcano (Figure 3). The limited evidence of volcanic activity (volcanic ash, lava fows, or volcanic debris) in the area creates doubt that the Tower was part of a volcanic system. It is possible that this material may simply have eroded away. In 2015, geologist Prokop Závada and his colleagues proposed their own hypothesis for the formation of the Tower. They compared it to a similar butte formation in the Czech Republic. Their hypothesis suggests that the Tower is the result of a maar-diatreme volcano (Figure 4). These form when magma encounters groundwater beneath the Earth’s surface. The super-heated water becomes steam. This steam expands explosively creating a crater on the surface. The crater fills with lava which cools and solidifes into a dome structure. Erosion wears away portions of the dome to create the Tower as we see it today.
The concept of erosion exposing the Tower is common to all of its modern formation theories. Ironically, the erosion which exposed the Tower also erased the evidence needed to determine which theory of Devils Tower’s formation is the correct one.
Explanation: