Answer:
[A] = 8.69x10⁻⁵g
Explanation:
Kinetics law of a radioactive atom, A, is:
Ln[A] = -kt + ln[A]₀
Where [A] could be taken as mass of A after time t (In seconds),
k is rate constant = ln2 / Half-Life
[A]₀ is intial mass of A
k = ln2 / 14.9s = 0.04652s⁻¹
Time in seconds:
5min * (60s / 1min) = 300s
Replacing each value:
ln[A] = -0.04652s⁻¹*300s + ln[100.0g]
ln[A] = -9.35
[A] = 8.69x10⁻⁵gIn atomic solids where the lattice points are occupied by Group 8 ( 18) atoms, the atoms are held together by __________ forces.
Answer:
London dispersion forces
Explanation:
There are different forces of attraction that helps to hold atoms or Molecules of a particular substance together. Some of the forces of attraction are ionic/ electrovalent bond, covalent bond, vander waals forces of attraction and so on.
Under the vander waals forces of attraction we have what is known as the London dispersion forces. This force of attraction is a very weak and it is commonly found in the atoms of noble gases.
The intermolecular force of attraction in which we are talking about that is london dispersion forces is formed as a result of the formation of non-polar dipoles which are not permanent.
Suppose an astronaut floating in space throws a rock. What will happen to the rock?
The half-life of the radioisotope 158Eu is 0.77 h. How much time is required for a 160.0-g sample of 158Eu to decay to 2.07 g?
a. 3.0 h
b. 4.0 h
c. 6.0 h
d. 2.1 h
e. 4.8 h
Answer: e. 4.8 h
Explanation:
Expression for rate law for first order kinetics is given by:
[tex]t=\frac{2.303}{k}\log\frac{a}{a-x}[/tex]
where,
k = rate constant
t = age of sample
a = let initial amount of the reactant
a - x = amount left after decay process
a) for rate constant
Half life is the amount of time taken by a radioactive material to decay to half of its original value.
[tex]t_{\frac{1}{2}}=\frac{0.693}{k}[/tex]
[tex]k=\frac{0.693}{0.77hr}=0.9hr^{-1}[/tex]
b) for 160.0 g to decay to 2.07 g
[tex]t=\frac{2.303}{0.9}\log\frac{160.0}{2.07}[/tex]
[tex]t=4.8hr[/tex]
The time required for a 160.0-g sample of 158Eu to decay to 2.07 g is 4.8 hours
Can someone answer 4 for me please?
During homogeneous catalysis, if a catalyst is present in the liquid phase, which phase must the reactants be in?
Answer:
The reactants must be in the liquid phase.
Explanation:
Homogeneous means that something is of the same nature.
In the context of catalysis, it means that the catalyst and the reactants are in the same phase.
If the catalyst is in the solid phase, the reactants are solids are well.
If the catalyst is in the liquid phase, then the reactants are also in the liquid phase.
And so on.
how many molecules of nitrogen are in 1.25 mol N2?
Answer:
7.52 x 10²³ molecules N
Explanation:
multiply 1.25 mol of N2 by Avogadro's Number
Which total mass is the largest?
(A) The mass of 2 electrons
(B) The mass of 2 neutrons
(C) The mass of 1 electron plus the mass of 1 proton
(D) The mass of 1 neutron plus the mass of 1 electron
Answer: B
Explanation: because the subatomic particle with the largest mass is the neutron.
Determine the bond orders, relative stabilities, and magnetic properties of the peroxide ion, and the superoxide ion.
Answer:
See explanation
Explanation:
The molecular orbital configuration of the super oxide ion is;
σ1s2, σ*1s2, σ2s2, σ*2s2, σ2px2, π2py2, π2pz2, π*2py2, π*2pz1
The molecular orbital configuration of the peroxide ion is;
σ1s2, σ*1s2, σ2s2, σ*2s2, σ2px2, π2py2, π2pz2, π*2py2, π*2pz2
Hence the bond order of the superoxide ion is 1.5 while the bond order of the peroxide ion is 1.
The superoxide ion is paramagnetic while the peroxide ion is diamagnetic.
Since the superoxide ion has a greater bond order and will have resonance structures as a result of its fractional bond order, it is more stable than the peroxide ion.
which two changes of state can be caused by removing thermal energy from a substace A. deposition B. condencation C. vaporization D.sublimation
Answer:
maybe is b but wait to other people answer
Answer:A. deposition B. condencation
Explanation:
Please help!! On a timer!! If you can help me with any of the following questions please, I'm lost.
1. What is the density of a block of marble that occupies 251 cm^3 and has a mass of 933 g? Answer in units of g/cm^3
2. Lee pushes horizontally with a force of 45 N on an 18 kg mass for 12 across the floor. Calculate the amount of Lee did. Answer in units of J.
3. What is the mass number of an element with atomic number 10 and 10 neutrons.
Answer:
3. Answer= Neon (Ne) is the Group 8A chemical element that has atomic number 10 and mass 20.1797.
A compound with a formula mass of 45.08 g/mol is found to be 85.64% Carbon and the remainder Hydrogen. Find the molecular formula:
Which is an example of a compound? * He3 or H2O or C
Answer:
H2O
Explanation:
There is more than one element
Select the correct definition below for the vocabulary term Oxygen
Answer:
Explanation:
We should be offered choices since you were offered some. However I will take a chance on what you should answer.
Oxygen is a non metal. Its most common charge is -2 which means that it has taken on two electrons. It is associated with fire and is an oxidizing agent which is a substance that will take on electrons). It is very reactive.
A student in chemistry class mixes two clear solutions together. Which of the following is the best evidence that a chemical reaction has occurred?
Question 5 options:
The solutions are soluble when mixed together.
The volume of the liquids increased.
A Yellow precipitate is formed when mixed together.
One liquid is insoluble in the other liquid.
Answer:
a yellow precipitate is formed when mixed together
A student in chemistry class mixes two clear solutions together. Then, a Yellow precipitate is formed when mixed together.
What is the solution ?A particular kind of homogenous combination made up of two or more components is known as a solution. A solute is a material that has been dissolved in a solvent, which is the other substance in the combination.
In a combination called a solution, every component is well combined. Solutions can contain solids, liquids, and gases and are regarded as homogenous mixes. A solute plus a solvent makeup a solution. Any material that dissolves in a solvent is referred to as a solute.
Solid, liquid, and gaseous solutions can be classified as solutions based on the physical states of the solvent and solute. Both the solute and the solvent are in the solid state in solid solutions.
Thus, option C is correct.
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Question 3 of 25
What is another name for Group 14?
Answer:
4A
Explanation:
on the periodic table
Chemicals that control weeds are called
A. acaricides.
B. herbicides.
C. insecticides.
D. pesticides.
Answer:
The answer is D
Explanation:
because insecticides are used for insects but pesticides are used to kill off unwanted plants
Answer:
B. herbicides
Explanation:
it kills weeds.
A sample of gas occupies a volume of 350.0 mL at 840mm Hg and 33°C. Determine the volume of this sample at 600 mm By and 52°C
Answer:
V₂ = 520.42 mL
Explanation:
Given data:
Initial volume = 350.0 mL
Initial pressure = 840 mmHg
Initial temperature = 33°C (33 +273 = 306 K)
Final temperature = 52°C (52+273 = 325 K)
Final volume = ?
Final pressure = 600 mmHg
Formula:
P₁V₁/T₁ = P₂V₂/T₂
P₁ = Initial pressure
V₁ = Initial volume
T₁ = Initial temperature
P₂ = Final pressure
V₂ = Final volume
T₂ = Final temperature
Solution:
V₂ = P₁V₁ T₂/ T₁ P₂
V₂ = 840 mmHg × 350.0 mL × 325 K / 306 K × 600 mmHg
V₂ = 95550000 mmHg.mL.K /183600 K.mmHg
V₂ = 520.42 mL
What is the visual differences between elements compounds and mixtures
Answer: yes I can do that tomorrow
Explanation:
A sample of wax requires heat to melt and become a liquid. What type of process is this?
Question 12 options:
A)
Deposition
B)
Sublimation
C)
Exothermic
D)
Endotherm
Answer:
D) Endothermic
Explanation:
An endothermic reaction absorbs heat. In this case, the wax absorbs the heat and it melts.
Also, I took the exam and I got it right.
Answer:
Endothermic is correct
How many atoms are in 2.37 moles of Krypton
Answer:
1.43 × 10²⁴ atoms Kr
General Formulas and Concepts:
Chemistry - Atomic Structure
Using Dimensional AnalysisAvogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.Explanation:
Step 1: Define
2.37 mol Kr
Step 2: Convert
[tex]2.37 \ mol \ Kr(\frac{6.022 \cdot 10^{23} \ atoms \ Kr}{1 \ mol \ Kr} )[/tex] = 1.42721 × 10²⁴ atoms Kr
Step 3: Check
We are given 3 sig figs. Follow sig fig rules and round.
1.42721 × 10²⁴ atoms Kr ≈ 1.43 × 10²⁴ atoms Kr
Need help please? Thanks youu
Answer:
A
B
E
Explanation:
"Fission is the splitting of a heavy, unstable nucleus into two lighter nuclei
and fusion is the process where two light nuclei combine together releasing vast amounts of energy"
a process that releases energy is respiration
The density of aluminum is 2.7 g/cm3 and that of Al2O3 is about 4 g/cm3. Calculate the PB ratio for Aluminum. (Hint: The Pilling-Bedworth Ratio (PBR) gives the volume of oxide formed to the volume of metal atoms.)
a) 1.28
b) 0.28
c) 0.75
Answer:
1.28
Explanation:
Al = aluminium
Density of Al = 2.7g/cm³
Density of Al2O3 = 4g/cm³
Molecular weight of Aluminum = 27g/mol
Molecular weight of Al2O3= 101.96 g/mol
Pilling bedworth ratio = Rob
= M(Al2O3) * density of Al / n* molecular weight of Al * density of Al2O3
= 101.96g/mol x 2.7g/cm³/2x 27g/mol x 4g/cm³
= 275.292/216
= 1.28
From the calculation above 1.38nis the PB ratio for aluminum
Which of the following statements are FALSE of models? (select all that applies)
A.) A scientific model must show one or more mechanisms that can explain what causes certain observations.
B.) It is possible to represent all of the components and relationships of a phenomenon.
C.) Models are revised many times as new information is gained.
D.) Models are completely accurate because choices have to be made to simplify the model.
E.) When creating a model, t is important to include the components that play a significant role in explaining the phenomenon or answering the question.
F.) Models must explain or make predictions about observations.
Answer:
A B and C
Explanation:
Hopefully this helps
Balanced or Unbalanced
K+2MgBr=KBr+Mg
The table shows the total number of electrons in Atom A and Atom B.
Atom Number of Electrons
A 11
B 17
Which statement is correct?
A. A will give up electrons to form bonds.
B. B will give up electrons to form bonds.
C. Both A and B will be chemically unreactive.
D. Both A and B will gain electrons to become stable
Answer:
C. Both A and B will be chemically unreactive.
Explanation:
Just took the test.
Using the K, L, M, N electronic configuration, both Atoms A and B do not have a full valence electron, hence, Both A and B will be chemically unreactive.
Atom A :
Number of electrons = 11
K - shell = 2
L - shell = 8
M - shell = 1 (valence shell is not complete)
Atom B :
Number of electrons = 17
K - shell = 2
L - shell = 8
M - shell = 7 (valence shell is not complete)
Atom A will give up electron to attain stability Atom B will gain electron to attain stabilityTherefore, Atoms A and B are chemically unreactive as they do not have a full valence electron.
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What is the frequency of visible light which has a wavelength of 625nm?
Answer:
The answer is 4.80 x 1014s-1b
Explanation:
625 nm x 10-9m= 6.25 x 10-7 m = c = 2.998 x 108m/s1 nm 6.25 x 10-7m=4.80 x 1014s-1b.)
The frequency of visible light is equal to 4.8 ×10¹⁴s⁻¹.
What are frequency and wavelength?Frequency can be described as the number of oscillations of a wave in a time of one second. The frequency of the wave or light has S.I. units which are per second (s⁻¹) or hertz.
Wavelength can be defined as the distance between the two adjacent points of a wave in the phase with each other. Two adjacent crests or adjacents troughs on a wave are separated by a distance is called wavelength.
The relationship between the speed of light, frequency, and wavelength is:
c = νλ
Given, the wavelength of the light, λ = 625nm = 625 × 10⁻⁹ m
Then we know that the speed of light, c = 3 × 10⁸ ms⁻¹
The frequency of the light can be calculated from the above-mentioned equation:
The frequency of the given visible light will be equal to:
ν = c/λ = 3× 10⁸ ms⁻¹/625 × 10⁻⁹ m = 4.8 ×10¹⁴ Hz
Therefore, the frequency of visible light is equal to 4.8 ×10¹⁴ Hz.
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If the gold in the crown was mixed with a less-valuable metal like bronze or copper, how would that affect its density?
Answer: If the gold in the crown was mixed with a less-valuable metal such as bronze of copper then this affects its density by making it to weigh even more and if it weighs more then it has less of chance to float. Observe: Drag each of the crowns into the liquid.
Explanation:
Density can be defined as the compactness of any substance. It is the mass/volume of a substance.
The density of gold is 19.3 g/ccThe density of copper is 9 g/ccThe density for bronze is 8.73 g/cc.Thus, if the gold crown is mixed with cheaper substances, such as bronze and copper, the density of the crown will decrease and it will become lighter.
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What is the net ionic equation for the acid-base reaction between chlorous acid and sodium hydroxide?
Answer: [tex]HCO_2(aq)+OH^-(aq)\rightarrow ClO_2^-(aq)+H_2O(l)[/tex]
Explanation:
Neutralization is a chemical reaction in which an acid and a base reacts to form salt and water.
Spectator ions are defined as the ions which does not get involved in a chemical equation or they are ions which are found on both the sides of the chemical reaction present in ionic form.
The reaction of chlorous acid (weak acid) and sodium hydroxide (strong base) is written as:
[tex]HClO_2(aq)+NaOH(aq)\rightarrow NaClO_2(aq)+H_2O(l)[/tex]
The equation can be written in terms of ions as:
[tex]HClO_2(aq)+Na^+(aq)+OH^-(aq)\rightarrow Na^+(aq)+ClO_2^-(aq)+H_2O(l)[/tex]
The ions which are present on both the sides of the equation are sodium ions and hence are not involved in net ionic equation.
Hence, the net ionic equation is :
[tex]HCO_2(aq)+OH^-(aq)\rightarrow ClO_2^-(aq)+H_2O(l)[/tex]
What is the molarity of a 5mol solution in 3L?
Answer:
1.67 M.
Explanation:
M = mol/L ⇒ M = 5mol / 3L = 1.67 M
Most elements are __ at room temperature
Answer:
Most elements are Solids at room temperature
