55.92 percent is the correct answer for online chemistry I just took the test!
Answer:
Explanation:
The best choice to prepare a buffer of pH 9.0 is a conjugate acid/base pair in which the acid has pKₐ = 9.0 ± 1.
Let's examine each of the choices.
A. NH₃/NH₄Cl
For NH₃, = pK_b = 4.75
For NH₄⁺, pKₐ 14.00 - 4.75 = 9.25
B. HCHO₂/NaCHO₂
For HCHO₂, pKₐ = 3.74
C. C₅H₅N/ C₅H₅NHCl
For C₅H₅N, = pK_b = 8.76
For C₅H₅N⁺, pKₐ 14.00 – 8.76 = 5.21
D. HNO₂/NaNO₂
For HNO₂, pKₐ = 3.33
The only acid with a pKₐ close to 9.0 is the ammonium ion.
The best buffer to prepare a buffer with pH 9.0 is
From the given options, the best combination to prepare a buffer with a PH of 9.0 is given by;
Option 1; NH₃;NH₄Cl
Now, we want to find the best choice to prepare a buffer of pH 9.0. Thus, let us look at each option;
Option 1; NH₃;NH₄Cl
We are given that pK_b for NH₃ is 4.75
Thus pKₐ for NH₄ is;
NH₄; pKₐ = 14.00 - 4.75
NH₄; pKₐ = 9.25
Option 2; HCHO₂; NaCHO₂
We are given that pK_a for HCHO₂ is 3.74
HCHO₂; pKₐ = 3.74
Option 3;C₅H₅N; C₅H₅NHCl
We are given that pK_b for C₅H₅N is 8.76
Thus
For C₅H₅N, = pK_b = 8.76
Thus, pKₐ for C₅H₅N is;
C₅H₅N; pKₐ = 14.00 – 8.76
C₅H₅N; pKₐ = 5.21
Option 4; HNO₂;NaNO₂
We are given pKₐ for HNO₂ as 3.33
HNO₂; pKₐ = 3.33
Looking at all the pKₐ values, the only acid that has a pKₐ close to 9.0 is NH₄ with a pKₐ of 9.25.
In conclusion, the best combination to prepare a buffer with pH of 9.0 is
NH₃;NH₄Cl
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by a lowercase letter. This tells you the types of elements in the compound.
Answer:
Elements
Explanation:
The elements which are represented by a single uppercase letter, or represented by an uppercase letter followed by a lowercase letter. This tells you the types of elements in the compound.
Elements are one of the simplest chemical substances that cannot be decomposed in a chemical reaction or by any chemical means. They are made up of small indivisible particles called atoms, all having the same number of protons.
Chemical symbols which can be single uppercase or one uppercase followed by a lowercase letter, are used in Chemistry to represent elements. They are used in the composition of compounds. For example, 'H' for Hydrogen and 'Ca' for Calcium.
In Chemistry, elements are represented by one or two letters. The first letter is always uppercase and the second letter, if present, is lowercase. These are known as chemical symbols and they correspond to the elements in the Periodic Table. For instance, the symbol for Hydrogen is H, and for Calcium it's Ca. These symbols are used to denote elements in chemical compounds. For example, water (H2O) is a compound consisting of Hydrogen and Oxygen.
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(2) Na2SO4 (4) NaSO4
A tree getting struck by lightning, it is an example of a physical change.
It is so because when a tree getting struck by lightning, it encountered a strong force of power but no new substance is formed here. So it is a physical change, if it is a chemical change then a new substance must formed here. So when a tree getting struck by lightning, it is an example of a physical change.
A tree getting struck by lightning involves both physical and chemical changes but the most prominent change is physical due to the visible damage and the instant vaporization of the tree's sap.
When a tree is struck by lightning, both physical and chemical changes occur. The lightning's immense heat can cause the sap inside the tree to instantly turn into vapor which results in a physical change. Additionally due to the lightning's high temperature, some of the tree's matter could possibly undergo chemical reactions such as combustion, leading to new matter being produced, which is a chemical change.
However the most prominent change observed is physical, as the visible damage to the tree and the immediate change from solid to vapour state of the sap are the most noticable effects. Thus, in essence a tree getting struck by lightning mainly causes a physical change.
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AND A BRAINIEST!!!
PLEASE I HAVE OTHER HW TO DO:(
Answer:
Explanation:
1. q=mcat
q = (20)(4.184)( 30-20)
q = 836.8