The decay of this radioactive unknown compound is a first-order process.
We can express the time dependence of its mass m using a first-order integrated rate law, where k is the rate constant:
[tex]m_t=m_0xe^{-kxt}[/tex]mt = mass at time t
m0 = initial mass
t = time
-----------------------------------------------------------------------------------------------------
Procedure:
1) We need to find "k":
From the first-order rate law we clear k,
[tex]\begin{gathered} \frac{m_t}{m_0}=\text{ }e^{-kxt} \\ \ln (\frac{m_t}{m_0})=\text{ -kxt} \\ \frac{\ln (\frac{m_t}{m_0})}{-t}=\text{ k} \end{gathered}[/tex][tex]k\text{ = }\frac{\ln (\frac{86.96ng}{695.7ng})}{-47}=0.044days^{-1}\text{ }[/tex]----------------------------------------------------------------------------------------------
2) We find the half-life from the value of k we have just calculated:
[tex]t_{\frac{1}{2}}=\text{ }\frac{\ln 2}{k}=\text{ }15.7\text{ days}[/tex]-----------------------------------------------------------------------------------------------
3) The number of half-lives of the unknown sample is:
Number of Half-lives = 47 days / 15.7 days = 3 (approx.)
Answer: Number of half-lives = 3
A gas occupies a constant volume at 35.0 celsius and 97 kPa. What is the pressure of the gas when the temperature is increased to 75 celsius?
For this question we are going to use Gay-Lussac's Law, which is an experimental gas law that shows the relationship between temperature and pressure in a gas. The formula is:
P1/T1 = P2/T2
We have:
P1 = 97 kPa
T1 = 308 K, we need to use Kelvin
P2 = ?
T2 = 348 K
Now we add these values into the formula:
97/308 = P2/348
0.315 = P2/348
P2 = 109.6 kPa, this will be new pressure
Chapter 6 Question 34 - AlgorithmicThe element that has a valence configuration of 3s2 3p6 is ________.- Choices:ArRnKrNeXe
We have to remember the rules to determine to which period and which group belongs an element, depending on its electronic configuration:
We always have to see the last level of energy, in this case is 3 (the highest number in the electronic configuration). It determines the period (the horizontal lines)
Now, we have to see the last letter which is with the 3, in this case the letter is p. It determines that the element is part of the A groups of the periodic table, also called the representative groups. In case of ending in d, it means that the element belongs to the transition metals. And trhe last possibility is ending in f, it means that the element belongs to the lanthanides and actinides.
The last thing, is to add up the valence electrons. Those are the ones in the last energy level, that as we mentioned before, it is 3 in this case. So, we have to add up, the exponents of the different letters that are in the last energy level. In this particular case, are the 2 and the 6, which is equal to 8.
So, we have to search in the periodic table, the element which is in the period 3, group VIII A. If we go, we will find it is the argon (Ar)
This type of bond is between two metals described as a "Sea of Electrons'?
Answer:
In the early 1900's, Paul Drüde came up with the "sea of electrons" metallic bonding
2.65 moles of an ideal gas at 36.9oC and 40,205Pa occupy 54.7mL. Additional gas is added to this container such that the temperature and pressure change to 113.7oC and 131,874Pa, with the volume remaining the same. How many moles of this gas were added?
The moles of gas added could not be determined because of an apparent error in the data provided for the volume of the container.
What is the number of moles of gas in the container?The moles of gas in the container is calculated from the ideal gas equation as follows;
PV = nRTn = PV / RTData given:
P = 131,874 Pa or 131.874 kPa
V = 54.7 mL = 0.0547 L
T = 113.7 °C or (113.7 + 273) K
T = 386.7 K
R, molar gas constant = 8.314 L⋅kPa.K/mol
n = (131.874 * 0.0547 L) / (8.314 * 386.7 )
n = 0.000224 moles
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- 47 Celsius to kelvin
Answer
226 K
Explanation
To change from C to K, you add 273
Therefore -47 C + 273 = 226 K
T
What is the balanced, net ionic equation for the reaction described below?Aqueous sodium phosphate and aqueous iron (III) chloride react to produce aqueous sodium chloride and solid iron (III) phosphate.
A net ionic equation is the one that only includes the ions that are involved in the formation of the solid.
According to the information the solid formed is iron (III) phosphate, and the ions involved are Fe3+ and PO43-.
It means that the net ionic equation is:
[tex]Fe_{(aq)}^{3+}+PO_{4(aq)}^{3-}\rightarrow FePO_{4(s)}[/tex]The correct answer is the second choice.
Calculate the pH if [H+] = 2.79 x 10^-11 M
Answer:
10.6.
Explanation:
What is given?
[H⁺] = 2.79 x 10⁻¹¹ M.
Step-by-step solution:
Let's see the formula of pH:
[tex]pH=-\log_{10}[H^+]=-\log_{10}[H_3O^+].[/tex]Where [H⁺] is the proton concentration in M. So we have to replace the given data in the formula:
[tex]pH=-\log_{10}{}\lbrack2.79\cdot10^{-11}]=10.55\approx10.6.[/tex]The pH of a [H⁺] = 2.79 x 10⁻¹¹ M solution would be 10.6.
What is true about the atoms at the start of a chemical reaction compare to the atoms at the end of a net reaction?
The question requires us to comment on what happens to the atoms in a chemical reaction considering the Law of Conservation of Mass.
The Law of Conservation of Mass states that mass is neither created nor destroyed in a chemical reaction. In other words, although the atoms in the reactants rearrange in order to form the products, the mass of both products and reactants must be the same.
Therefore, we can say that, considering the Law of Conservation of Mass, the atoms at the start of a chemical reaction are rearranged compared to the atoms at the end of the reaction, but the mass of reactants and products do not change.
A process that may lead to gamates containing too many or too few chromosomes is called?
(A) Recombination
(B) Crossing over
(C) Karyogenesis
(D) Nondisjunction
Answer:
D) Nondisjunction
Explanation:
Nondisjunction happens when a chromosome pair doesn't separate during meiosis. A result is one of the gamates has to any chromosome, while others have much less.
what are the limiting and excess reactants when 26.62 moles of FeS2 react with 59.44 moles of O2
Step 1
The reaction must be completed and balanced as follows:
4 FeS2 + 11 O2 => 2 Fe2O3 + 8 SO2
-------------------------
Step 2
Information provided:
26.62 moles of FeS2
59.44 moles of O2
-------------------------
Step 3
The limiting and the excess reactant
Procedure: by stoichiometry,
4 FeS2 + 11 O2 => 2 Fe2O3 + 8 SO2
4 moles FeS2 ------------ 11 moles O2
26.62 moles FeS2 ------------ X
X = 26.62 moles FeS2 x 11 moles O2/4 moles FeS2
X = 73.20 moles
For 26.62 moles of FeS2, 73.20 moles of O2 are needed, but there are only 59.44 moles so the limiting reactant is O2, and the excess reactant is FeS2.
Answer:
The limiting reactant = O2
The excess reactant = FeS2
An experiment begins
with 87.5g of
potassium and 13.2g of
chlorine. What is the
experiment mass of
the product?
The experiment mass of the product is 28.1g
What is mass ?
Mass is a physical body's total amount of matter. It also serves as a gauge for the body's inertia, or resistance to acceleration (change in velocity) in the presence of a net force. The strength of an object's gravitational pull to other bodies is also influenced by its mass.
The kilogramme is the primary mass unit in the SI (kg). Although weight is frequently measured using a spring scale rather than a balancing scale and compared directly with known masses, mass is not the same as weight in physics.
2K + Cl2 =====> 2KCl
70g Cl2 produces 2(39+35.5) = 149 g KCl
13.2g Cl2 produces 28.1g KCl
the experiment mass of the product is 28.1g
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What type of bond is formed between hydrogen and oxygen atoms within a water molecule?Ionic bondNonpolar covalent bondPolar covalent bondHydrogen bondWhich of the following best describes a solute that is dissolved in water?Aqueous solutionGaseous solutionAlloyHeterogeneous solution
To determine what type of bond is formed when hydrogen and oxygen form water, we have to find the difference in electronegativities of hydrogen and oxygen:
[tex]3.44-2.2=1.24[/tex]According to this, the difference between electronegativities is less than 1.7 and greater than 0.4, which means that the type of bond formed by oxygen and hydrogen is polar covalent bond.
Consider the following reaction in the forward direction. Identify the base:
CH₃O⁻ + H₂O ⇌ CH₃OH + OH⁻
If we consider the reaction CH₃O⁻ + H₂O ⇌ CH₃OH + OH⁻ in the forward direction, the base in the reaction is CH₃O⁻
A compound can be acidic, basic or neutral in nature. Basicity of the compound is determined when it either releases hydroxide ions, donates electrons or else accepts the protons from a compound.
In the reaction CH₃O⁻ + H₂O ⇌ CH₃OH + OH⁻:
CH₃O⁻ accepts proton or [H+] ion to become CH₃OH. Thus, CH₃O⁻ is the base in the reaction
H₂O donate [H+] ion or proton, therefore H2O change into OH-. Thus, H₂O is an acid in the reaction.
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Two different signs that indicate a chemical action has occurred. What time is showing in the picture on the left what sign is showing on the picture in the right?
The reaction that occurs on the left is called a single displacemt reaction
What volume of carbon dioxide (in L) will 2.00 g of antacid made of calcium carbonate produce at 37.0 °C and 1.00 atm in the stomach according to the following reaction?
CaCO₃ (s) + 2 HCl (aq) → CaCl₂ (aq) + H₂O (l) + CO₂ (g)
The volume of carbon dioxide (in L) that can be made from the 2.00 g of the antacid is 5.09 L
How to determine the volume of CO₂We'll beging by obtaining the mole of CO₂ produced. This can be obtained as follow:
Mass of CaCO₃ = 2 gMolar mass of CaCO₃ = 100 g/mole Mole of CaCO₃ = 2 / 100 = 0.02 moleCaCO₃ (s) + 2 HCl (aq) → CaCl₂ (aq) + H₂O (l) + CO₂ (g)
From the balanced equation above,
1 mole CaCO₃ reacted to produce 1 mole of CO₂.
Therefore,
0.02 mole CaCO₃ will also react to produce 0.02 mole of CO₂.
Finally, we shall determine the volume of the CO₂ produced. Details below.
Number of mole (n) = 0.02 moles Pressure (P) = 1 atm Temperature (T) = 37 °C = 37 + 273 = 310 KGas constant (R) = 0.0821 atm.L/Kmol Volume (V) =?PV = nRT
1 × V = 0.02 × 0.0821 × 310
V = 5.09 L
Thus, the volume obtained is 5.09 L
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Which two types of information are written in an element's box in the periodic
table?
A. Atomic mass
B. Number of electron shells
C. Nuclear composition
D. Chemical symbol
Answer:
b d my good mannnnnnnnnnnn
How much water needs to be added to 65 mL of 3.0 M stock solution to produce a 1.0 M diluted solution?
To answer this question, we have to use the dilution rule, that is represented by the following equation:
[tex]C1V1=C2V2[/tex]Where C1 and C2 are the initial and final concentrations and V1 and V2 are the initial and final volumes.
Solve the equation for V2 to find the final volume:
[tex]\begin{gathered} V2=\frac{C1V1}{C2} \\ V2=\frac{3.0M\cdot65mL}{1.0M} \\ V2=195mL \end{gathered}[/tex]The final volume of the solutions has to be 195mL. Since we already have 65mL, we need to add 130mL of water to have 195mL in total.
It means that the correct answer is 130mL.
An intravenous a solution to replace potassium loss contains 35mEq/L each of K+and CL- . How many moles of CL- are in 1.8 L of the solution
The moles of Cl⁻ ions present in 1.8 L of the intravenous solution is 0.063 moles.
What are the moles of Cl⁻ ions in the intravenous solution?The moles of Cl⁻ ions in the intravenous solution are calculated using the conversion factor between mEq/L to mmoles
The conversion between milliequivalents per Liter and millimoles per Liter is:
1 Millimole per Liter = 1 Milliequivalents per Liter.
Hence 35 mEq/L = 35 mmol/L
The mmoles of Cl⁻ ions in 1.8 liters of the intravenous solution will be:
moles of Cl⁻ ions = 35 mmol/L * 1.8 L
moles of Cl⁻ions = 63 mmoles
Converting to moles by dividing by 1000:
moles of Cl⁻ ions = 63 / 1000
moles of Cl⁻ ions = 0.063 moles.
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Electrons in atoms exist in particular energy levels. A _______ must be emitted or absorbed to move between energy levels.Question 19 options:A) photonB) electronC) particleD) quantum
Answer: We can complete the sentence as:
"Electrons in atoms exist in particular energy levels. A photon must be emitted or absorbed to move between energy levels" (letter A).
Explanation:
The question requires us to choose the best option to complete the sentence: "A ________________ must be emitted or absorbed to move between energy levels".
Energy levels are fixed distances from the nucleus of an atom where electrons can be found. Energy levels can be compared to stairs in a staircase: we can stand on a step, on the previous step or the next step, but never between them; this is what happens to electrons, as they can occupy one energy level or another but not the space between energy levels.
To move from one energy level to another, an electron must absorb energy (to move to a higher level) or emit energy (to move to a lower level). The energy difference between a lower starting level and a higher ending level must correspond to the energy of a photon of light absorbed in order to make the transition between energy levels possible. Additionally, electrons are usually unstable at excited states (when at a higher energy level that it was initially), and the electron quickly returns to the lower energy level emitting the excess of energy in the form of light (as a photon of light).
Therefore, considering the information above, we can complete the sentence as:
"Electrons in atoms exist in particular energy levels. A photon must be emitted or absorbed to move between energy levels" (letter A).
A single electron in an orbital has quantum numbers n = 2, ℓ = 0, mℓ = 0, ms = ½. what are the quantum numbers for the next electron added to this atom?
The quantum numbers for the next electron added to this atom are n = 2, ℓ = 0, mℓ = 0, ms = -½
The set of numbers used to explain the placement and strength of the electron in an atom are called quantum numbers. There are 4 quantum numbers, particularly, main, azimuthal, magnetic, and spin quantum numbers. The values of the conserved portions of a quantum gadget are given by quantum numbers.
The price of n tiers from 1 to the shell of the outermost electron of that atom. The important quantum variety may be determined by way of searching the period (numbered row) of the element on the periodic table. The principal quantum numbers of electrons inside the S-block and P-block are similar to the period range.
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In which of the following atoms does a 3p electron experience the greatest effective nuclear charge?
Question options:
P
Cl
Si
Ar
Al
Answer:
Ci
Explanation:
because it is an electron effective nuclear charge
How is chemical weathering different from physical weathering?(30 points)
Chemical weathering forms new substances, while physical weathering does not.
Chemical weathering involves plants and animals, while physical weathering does not.
Chemical weathering requires a reaction with water, while physical weathering does not.
Chemical weathering results in the breakdown of rock, while physical weathering does not.
Answer:
Chemical weathering results in the breakdown of rock, while physical weathering does not.
Explanation:
When a substance such as ice, rushing water, wind, rapid heating or cooling, or plant growth exerts force on a rock, it breaks the rock physically or mechanically. Chemical weathering is the process by which a substance dissolves a rock, resulting in the rock's fragments falling away.
Place the following gases in order of decreasing average molecular speed at 300K: He, SF6, SO2, Ar
Temperature is a way to measure the kinetic energy of the molecules of gases. The kinetic energy is a kind of energy that a moving body has. it is related to the mass of the body and the speed they are moving. The kinetic energy can be calculated as:
[tex]E_k=\frac{1}{2}mv^2[/tex]Where Ek is the kinetic energy, m is mass of the molecules and v is the speed of the molecule
Knowing that gasses with the same temperature have same kinetic energy, then gasses with larger mass will move slower and viceversa.
Since the molar mass of those gases are:
He: 4.00 g/mol
SF6: 146.06 g/mol
SO2: 64.066 g/mol and
Ar: 39.948 g/mol
the ligther gasses move faster and the hevier slower, so we just have to order them by increasing mass:
He, Ar, SO2 and SF6
Sulfur (S) has an atomic number of 16. What is the ground-state electron configuration of sulfur?
A dog
walks along the ground. If
the dog applies an action
force on the ground, what is
the reaction force?
Action and response are two forces that have the same magnitude but opposing directions.
Explanation.
The force used by a dog as it moves across the ground is known as the action force. The force that the earth exerts on the dog is the reaction force, on the other hand. Newton's third law of motion serves as its foundation.
What does walking on the ground include action and reaction force?When we walk on the ground, we push the earth backward with our feet, but the ground pushes our feet forward with an equal force, which propels us forward. Because of this, the action is the force that pushes the ground backward, and the reaction is the force by the ground on our feet.
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What has happened in the field of forensics in the past few decades?
A.
Very few members of the public have heard of a case dealing with forensics.
B.
The use of forensics is more popular with the public and law enforcement.
C.
Colleges have stopped offering courses and majors in forensic science.
D.
It has become completely detached from the criminal justice system.
Answer:
c
Explanation:
V atery few members of the public have heard of a case dealing with forensics. The use of forensics is more popular with the public and law enforcement. Colleges have stopped offering courses and majors in forensic science.
How many mols of Cl₂ are needed to make 0.6 mols of NaCl according to the
following reaction?
2Na + Cl₂ --> 2NaCl
A 500 g sample of Al2(SO4)3 is reacted with 450 g of Ca(OH)2. A total of 596 g of CasO4 isproduced. What is the limiting reactant in this reaction, and how many moles of excess reactantare unreacted? Al2(SO4)3 (ag) + 3Ca(OH)2 (ag) -> 2Al(OH)3 (s) + 3CaSO4 (s)
ANSWER
[tex]undefined[/tex]EXPLANATION
Given that;
The mass of Al2(SO4)3 is 500 grams
The mass of Ca(OH)2 is 450 grams
The mass of CaSO4 is 596 grams
Follow the steps below to find the limiting reactant of the reaction
Step 1; Write the balanced equation of the reaction
[tex]\text{ Al}_2(SO_4)_{3(aq)}+\text{ 3Ca\lparen OH\rparen}_{2(aq)}\text{ }\rightarrow\text{ 2Al\lparen OH\rparen}_{3(s)}\text{ + 3CaSO}_{4(s)}[/tex]In the reaction above, 1 mole Al2(SO4)3 reacts with 3 moles Ca(OH)2 to give 2 moles Al(OH)3 and 3 moles CaSO4
Step 2; Determine the number of moles using the below formula
[tex]\text{ mole = }\frac{\text{ mass}}{\text{ molar mass}}[/tex]Recall, that the molar mass of Al2(SO4)3 is 342.15 g/mol and the molar mass of Ca(OH)2 is 74.093 g/mol
For Al2(SO4)3
[tex]\begin{gathered} \text{ Mole = }\frac{500}{\text{ 342.15}} \\ \text{ Mole = 1.461 moles} \end{gathered}[/tex]For Ca(OH)2
[tex]\begin{gathered} \text{ Mole = }\frac{\text{ 450}}{\text{ 74.093}} \\ \text{ Mole = 6.073 moles} \end{gathered}[/tex]Step 3; Find the limiting reactant of the reaction
To find the limiting reactant of the reaction, divide the moles of the reactant by the co-efficient of the compound
[tex]\begin{gathered} \text{ For Al}_2(SO_4)_3 \\ \text{ The mole ratio = }\frac{1.461}{1} \\ \text{ The mole ratio = 1.461 mol/wt} \\ \\ \text{ For Ca\lparen OH\rparen}_2 \\ \text{ The mole ratio = }\frac{\text{ 6.073}}{3} \\ \text{ The mole ratio = 2.024 mol/wt} \end{gathered}[/tex]Since the limiting reactant of the reaction is the reactant with the lowest number of mol/wt, then Al2(SO4)3 is the limiting reactant
[tex]\text{ The limiting reactant of the reaction is Al}_2(SO_4)_3[/tex]The excess reactant of the reaction is Ca(OH)2
Therefore, the no of moles of the excess reactant that is unreacted is
6.073 - 1.461 = 4.612 moles
Hence, the number of moles of the excess reactant that is unreacted is 4.621 moles
A solution is made using 80.1 g of dimethyl ether (MM = 46.07 g/mol) and 110.0 g of methanol (MM = 32.04 g/mol). What is the molality of the dimethyl ether in the solution?
The molality of the dimethyl ether in the solution is 15.8m
What is molarity ?
Molality (m), or molal concentration, is the amount of a substance dissolved in a certain mass of solvent. It is defined as the moles of a solute per kilograms of a solvent.
Moles of dimethyl ether= 80.1/46.07 = 1.74 moles
Molarity = moles of solute/ mass of solvent * 1000
1.74/110*1000 = 15.8m
The molality of the dimethyl ether in the solution is 15.8m
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explain absolute entropies and it's determination in terms of heat capacity
The total entropy that a pure material would accumulate upon warming from absolute zero (where S=0) to the specific temperature is the absolute entropy of that substance at that temperature.
What is entropy?
One of the key ideas that students studying physics and chemistry need to grasp with clarity is entropy. More importantly, entropy has multiple definitions and can be used in a variety of contexts, including the thermodynamic stage, cosmology, and even economics. Entropy is a notion that mostly discusses the spontaneous changes that take place in commonplace phenomena or the universe's propensity for chaos.
Determination in terms of heat capacity
The third rule of thermodynamics has two significant ramifications: it establishes a constant reference point that enables us to measure the absolute entropy of any substance at any temperature, and it specifies the sign of the entropy of any substance at temperatures above absolute zero as positive. We look at two different approaches to calculating S for a reaction or a physical change in this section.
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