Answer:
λ(Decay constant) = 0.0492sec-¹
The relationship between Decay Constant and Half life (t½)
λ=0.693/t½
given the decay constant as 0.0492
We can get the Half life
t½ = 0.693/0.0492
t½= 14.09secs.
N = N°(½)ⁿ
Where N= Remaining Amount of the original Compound
N° = Original Amount of compound.
n is simply a tern used to represent the ratio of time taken/half life
In other words
n=t/t½
Given N°=0.656 mol/L
N=0.433mol/L
0.433 = 0.656(½)ⁿ
(½)ⁿ = 0.433/0.656
(½)ⁿ = 0.660
Taking the Natural Log(Ln) of both sides
Ln(½)ⁿ = Ln(0.66)
nLn(½) = -0.4155
n(-0.6931) = -0.4155
n= 0.4155/0.6931
n= 0.5995.
n = time/half life
t = half life x n
t = 14.09 x 0.5995
t = 8.45secs.
what is the zeff of carbon
Answer:
Explanation:
The steps to calculate the Zeff is :
1) Write the electronic configuration.
Carbon: 1s2 2s2 2p2
Oxygen: 1s2 2s2 2p4
2) there are two core electrons in each atom and four in carbon and six in oxygen.
1s) (2s2p)
3) as mentioned the shielding of electrons within the same shell is negligible.
4) for electron of s or p orbital the shielding contribution by the electrons having a principal quantum number less by one would be 0.85 each. And all electrons further left would contribute an amount of 1.0 each.
5) For oxygen:
Zeff = Z - S
S = 2X0.85 = 1.7
Zeff = 8- 1.7 = 6.3
For carbon
Zeff = Z - S
S = 2X0.85 = 1.7
Zeff = 6- 1.7 = 4.3
Someone help please I don’t know the answer to the question I meeed help
Answer: 143.3
137+115+104+263+98 divided by 5.Which gives us 143.3
Could someone help with this? Much appreciated!
Answer:
The 3rd answer down.
Na²O (sodium oxide) will be a base when exposed to water H²O
Explanation:
Sodium Oxide Na²O, will become Sodium Hydroxide after being exposed to water (at 80% I believe).
The oxygen ion in Na²O has 2 extra electrons which makes it highly charged and very attractive to hydrogen ions. The attraction is so strong that when Na²O comes in contact with H²O, the O(-2) strips off a hydrogen from water, forming 2 x OH ions which of course are still strongly basic.
a 67.5 L sample of gas at 27.6 °c and 383.1mm hg expands to 244.2 L at 4.7 °c. what is the new gas pressure.
a 97.8
b 18.0
c 115
d 1.65
Answer:
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How would you expect cesium, Cs, to react with water? explaining your reasoning.
Answer:
Caesium reacts rapidly with water to form a colourless basic solution of caesium hydroxide (CsOH) and hydrogen gas (H2).
Explanation:
The reaction continues even when the solution becomes basic. The resulting solution is basic because of the dissolved hydroxide. The reaction is exothermic.
If sodium chloride (NaCl) is dissolved in water, how will the vapor pressure of the water be affected?
A. The vapor pressure will be raised, making it more easier to boil.
B. The vapor pressure will be raised, making it more difficult to boil.
C. The vapor pressure will be lowered, making it easier to boil.
D. The vapor pressure will be lowered, making it more difficult to boil.
The vapor pressure will be lowered, making it more difficult to boil If sodium chloride (NaCl) is dissolved in water. Hence, option D is correct.
What is vapor pressure?It can be defined as the pressure exerted by a vapor with its condensed phases in a closed system at a given temperature show the equilibrium vapor is a well-known measure of a liquid evaporation rate.
The vapor pressure of a liquid is the point at which equilibrium pressure is reached in a closed container. The molecules leaving the liquid and going into the gaseous phase and molecules leaving the gaseous phase and entering the liquid phase.
It is measured in the standard units of pressure the international system of units. Pressure as a derived unit with the dimension of force per area and designate the Pascal (Pa) as its standard unit.
When common salt is dissolved in water boiling point of a solution increases the boiling point of a substance is the temperature at which it will be lowered, making it more difficult to boil If sodium chloride (NaCl) is dissolved in water. Hence, option D is correct.
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Which side of the chain should you count from when naming organic compounds?
Center
Right side
Left side
Side that will give you the longest Carbon chain
Side that will give you the longest carbon chain will be counted when naming organic compounds.
What is an Organic compound?These are chemical compounds that contain carbon-hydrogen or carbon-carbon bonds in their structure.
The longest carbon chain should be counted first to ascertain the type of compound to be named.
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What is Entropy?
A. The opposite of Enthalpy
B. The temperature at which a reaction is feasible.
C. A measure of disorder.
D. Free energy used for a reaction.
Answer:
C. A measure of disorder :)
The sugars can be classified as either aldoses or ketoses.
a. True
b. Fasle
The following two compounds each exhibit two heteroatoms (one nitrogen atom and one oxygen atom). In compound A, the lone pair on the nitrogen atom is more likely to function as a base. However, in compound B, the lone pair on the oxygen atom is more likely to function as a base. Explain this difference by selecting the correct reason(s)
Answer:
The answer is the photo attached
Explanation:
Explain why it is not advisable to add water to acid when
mixing them
Answer:
Consequence
you form an extremely concentrated solution of acid initially.and the solution may boil very violently, splashing concentrated acid. I hope this helped! :)An ion of a single pure element always has an oxidation number of ________.
A. None of these
B. magnitude equal to its atomic number
C. 1
D. 0
Answer:
0
Explanation:
pure elements will always possess an oxidation number of 0, regardless of their charge.
Answer:
D.) 0
Explanation:
I got it correct on founders edtell
An ionic bond is a bond
Answer:
That involve the complete transfer of an electron from one atom of an element to another
9.7300x10^2 + 9.8700x10^3
? × 10^?
Answer:
19.6 x 10⁵
1.96 x 10⁶
I hope it's helps you
If the starting material has no stereogenic centers, when carbonyl compounds are reduced with a reagent such as LiAlH4 or NaBH4 and a new stereogenic center is formed, what will the composition of the product mixture be?
A) Forms a racemic mixture of the two possible enantiomers.
B) Forms more of one enantiomer than another because of steric reasons around the carbonyl.
C) Forms more of one enantiomer than another depending on the temperature of the reaction.
D) Forms different products depending on the solvent used.
Answer:
A) Forms a racemic mixture of the two possible enantiomers
When carbonyl compounds are reduced with a reagent such as LiAlH₄ or NaBH₄ and new stereogenic center is formed chemical change will lead to products that form a racemic mixture of the two possible enantiomers.
What is a chemical change?
Chemical changes are defined as changes which occur when a substance combines with another substance to form a new substance.Alternatively, when a substance breaks down or decomposes to give new substances it is also considered to be a chemical change.
There are several characteristics of chemical changes like change in color, change in state , change in odor and change in composition . During chemical change there is also formation of precipitate an insoluble mass of substance or even evolution of gases.
There are three types of chemical changes:
1) inorganic changes
2)organic changes
3) biochemical changes
During chemical changes atoms are rearranged and changes are accompanied by an energy change as new substances are formed.
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Which of the following represents a physical change?
Answer:
» Water evaporating to gas.
» Solid subliming to gas.
» Water freezing to solid.
» Solid melting to liquid.
Explanation:
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Draw all four products when the following compound undergoes dehydrohalogenation and rank them in terms of stability. Which product do you expect to be the major product?
Answer:
2 Methyl pent 2 ene
5. Calcule las concentraciones cuando se alcanza el equilibrio si partimos de unas concentraciones iniciales [A]=[B]=1M ; [C]=[D]=0M y una constante de equilibrio de 5.
Las concentraciones en el equilibrio para la reacción química presentada son:
[tex][A] = [B] = 1-x = 1-0.69 = 0.31 M\\[C] = [D] = x = 0.69 M[/tex]
Consideremos la siguiente reacción química genérica:
A + B ⇄ C + D
Para calcular las concentraciones en el equilibrio, debemos construir una Tabla ICE. Cada fila representa una instancia (Inicial, Cambio, Equilibrio) y la completamos con la concentración o cambio de concentración ("x" para concentraciones desconocidas). Como inicialmente no hay productos, la reacción se desplazará hacia la derecha para alcanzar el equilibrio.
A + B ⇄ C + D
I 1 1 0 0
C -x -x +x +x
E 1-x 1-x x x
La constante de equilibrio, Kc, es:
[tex]Kc = 5 = \frac{[C][D]}{[A][B]} = \frac{x^{2} }{(1-x)^{2} } \\\sqrt{5} = x/1-x\\x = 0.69[/tex]
Las concentraciones en el equilibrio son:
[tex][A] = [B] = 1-x = 1-0.69 = 0.31 M\\[C] = [D] = x = 0.69 M[/tex]
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I 100 mL o a pharmaceutical preparation contains 20 mL o a 50% w/v solution o benzalkonium chloride, what is the percent strength o that agent in the solution
The percentage strength of the agent is 10 %
Since 100 mL of a pharmaceutical preparation contains 20 mL of a 50% w/v solution of benzalkonium chloride, we desire to find the percentage strength of that agent in the 100 mL solution.
Let C₁ = percentage strength of 20 mL solution = 50 %, V₁ = initial volume = 20 mL, C₂ = percentage strength of agent in 100 mL solution and V₂ = final volume = 100 mL.
Since the initial quantity of agent in 20 mL solution equals the final quantity of agent in 100 mL solution, we have that
C₁V₁ = C₂V₂
So, making C₂ = percentage strength of agent in 100 mL solution the subject of the formula, we have
C₂ = C₁V₁/V₂
Substituting the values of the variables into the equation, we have
C₂ = C₁V₁/V₂
C₂ = 50 % × 20 mL/100 mL
C₂ = 50 % × 0.2
C₂ = 10 %
So, the percentage strength of the agent is 10 %.
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help me in my hw,wt is physical change and chemical change Answer it asap plz don't spam
Answer:
Sorry but i don't undertsnad the question.
Explanation:
Answer:
A physical change is a change to the physical—as opposed to chemical—properties of a substance. They are usually reversible. The physical properties of a substance include such characteristics as shape, color, texture, flexibility, density, and mass.
A chemical change happens when one chemical substance is transformed into one or more different substances, such as when iron becomes rust.
Do u want examples ?
what is the bond energy required to break one mole of carbon-carbon bonds
Answer:
100 kcal of bond energy
A sample of water at 21.5°C required an input of 1.69 x 104 of heat to reach its boiling point, 100.0 °C. What was the mass of the
water?
What mass of water is formed in the reaction of 4.16g H with excess oxygen gas.
Answer:
Explanation:
Start with a balanced equation.
2H2 + O2 → 2H2O
Calculate mole H2 using the formula: n = m/M, where:
n = mole
m = mass (g)
M = molar mass (g/mol)
Calculate molar mass of H2.
M H2 = 2 × 1.008 g/mol = 2.016 g/mol
Calculate moles H2.
n H2 = 4.16 g H2/2.016 g/mol = 2.063 mol H2
Calculate moles H2O by multiplying moles H2 by the mole ratio between H2O and H2 from the balanced equation, so that moles H2 cancel.
2.063 mol H2 × (2 mol H2O/2 mol H2) = 2.063 mol H2O
The mass of water will be calculated by rearranging the n = m/M formula to isolate m;
m = n × M
Calculate the molar mass H2O.
M H2O = (2 × 1.008 g/mol) + (1 × 15.999 g/mol) = 18.015 g/mol
Calculate the mass H2O.
m = n × M = 2.063 mol H2O × 18.015 g/mol = 37.2 g H2O
4.16 g H2 with excess O2 will produce 37.2 g H2O.
a=bcd in order to solve the equation above for b you must multiply both sides of the equation by the same expression
a x _ = bcd x _
the results equation is:
b=
Both sides of the equation must be multiplied by 1/cd to give the following equation: b = a/cd
The following equation was given in this question: a = bcd. This means that a = b × c × d. Hence, to make "b" the subject of the formula, we have to eliminate "cd" from the side of the equation with "b". To do that, we multiply both sides of the equation with the same expression as follows:a x 1/cd = bcd x 1/cd
"cd" cancels out "cd" in the right side of the equation to result to:a/cd = b
Therefore, b = a/cd
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A(n) _____, used as part of the stationary phase, has an affinity for the solvent and the chemical components of the mixture. adsorbent eluent Rf factor chromatogram
The Adsorbent is used as part of the stationary phase and has an affinity for the solvent and the chemical components of the mixture.
The adsorbent has a high affinity for solvent and the chemical components of the mixture.
Chromatography is a method of separation in which the mixture of substances is introduced into a mobile phase (solvent). The separation occurs as the solvent interacts with an adsorbent(stationary phase).
The extent of separation of the components of the mixture depends on the extent of interaction between the mobile and the stationary phase . This interaction also determines the retention factor (Rf) of the separation.
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18. What is the density of a substance with a mass of 0.90 kg and a volume of 1.2 mL?
21. An oxygen tank in the lab has a pressure of 12 atm at 250C. If the pressure inside the gas tank exceeds 25 atm, the tank will explode. If a fire occurs in the lab, raising the temperature of the gas inside the cylinder to 398oC, will the tank explode?
Answer:
fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
Explanation:
Which phenomenon explained below is an example of deposition?
Select the correct answer below:
A) Hail is formed from water droplets lifted by air currents to an altitude where they turn into pellets of ice.
B) Frost forms when cold evening temperatures convert the humidity in the air to thin layers of ice on the ground.
C) In the winter, the top few inches of a pond turn to ice.
D) The visible cloud arising from a boiling tea kettle is not actually steam, but droplets of liquid water that form as the
steam cools in the air.
Answer:
b
Explanation:
deposition is when water turns from gas to solid. b is the only one that fits
Deposition is frost forms when cold evening temperatures convert the humidity in the air to thin layers of ice on the ground.
What is deposition?Deposition is a process that involves collection of large mass or when mean distance between molecules are reduced. It can also be explained as gathering of substances together to form a larger mass.
Therefore, the phenomenon explained in the given example about deposition is frost forms when cold evening temperatures convert the humidity in the air to thin layers of ice on the ground.
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What is the maximum number of electrons in the following energy level?
n = 4
Answer: 32 electrons
Explanation:
What volume of 6.9 M NaOH is needed to completely titrate 0.42 L of 2.39 M phosphoric acid according to
the equation:
H3PO4(aq) + 3NaOH(aq) + Na3PO4(aq) + 3H2O(aq)
A) O 0.05 L
B) O6.93 L
C) O0.44 L
D) 03.01 L
E) 436.43 L
Taking into account the definition of molarity and the stoichiometry of the reaction, the correct option is option C) 0.44 L of 6.9 M NaOH is needed to completely titrate 0.42 L of 2.39 M phosphoric acid.
The balanced reaction is:
H₃PO₄ (aq) + 3 NaOH (aq) → Na₃PO₄ (aq) + 3 H₂O(aq)
Then, by stoichiometry of the reaction (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of moles of each compound participate in the reaction:
H₃PO₄: 1 mole NaOH: 3 moles Na₃PO₄: 1 mole H₂O: 3 molesMolarity is the number of moles of solute that are dissolved in a given volume.
Molarity is determined by:
[tex]Molarity=\frac{number of moles of solute}{volume}[/tex]
Molarity is expressed in units [tex]\frac{moles}{liter}[/tex].
In this case, 0.42 L of 2.39 M phosphoric acid reacts. So, by definition of molarity, the number of moles that participate in the reaction is calculated as:
[tex]2.39 \frac{moles}{liter}=\frac{number of moles of phosphiric acid}{0.42 liters}[/tex]
Solving:
number of moles of phosphiric acid= 2.39 [tex]\frac{moles}{liter}[/tex]* 0.42 liters
number of moles of phosphiric acid= 1.0038 moles ≅ 1 mole
Approaching 1 mole of the amount of phosphoric acid required, then by stoichiometry of the reaction, 3 moles of NaOH are necessary to react with 1 mole of the acid.
Then by definition of molarity and knowing that 6.9 M NaOH is needed, you can calculate the necessary volume amount of NaOH by:
[tex]6.9 \frac{moles}{liter} =\frac{3 moles}{volume}[/tex]
Solving:
6.9 [tex]\frac{moles}{liter}[/tex]* volume= 3 moles
[tex]volume=\frac{3 moles}{6.9\frac{moles}{liter} }[/tex]
volume= 0.44 L
The correct option is option C) 0.44 L of 6.9 M NaOH is needed to completely titrate 0.42 L of 2.39 M phosphoric acid.
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Để xác định hàm lượng Cu trong hợp kim Cu-Zn người ta làm như sau: Hòa
tan hoàn toàn 2,068g mẫu hợp kim Cu-Zn trong lượng dư axit HNO3, thu được dung
dịch X. Đun đuổi axit dư, điều chỉnh tới pH 3 thu được 100mL dung dịch Y. Lấy
10mL dung dịch Y, thêm KI dư, rồi chuẩn độ dung dịch tạo thành bằng dung dịch
Na2S2O3 0,1M thì thấy hết 15,0 mL. Viết các phương trình phản ứng xảy ra. Tính
hàm lượng Cu trong mẫu hợp kim trên.
