Answer:
5 half lives
Explanation:
Given that
Thorium - 236 contains the half-life of 10.0 minutes
And there is 250 grams
We need to find out the number of half lives that took place after 50.0 minutes
As in the question
1 half life is 10 minutes
So for 50 minutes, it would be
= 50 minutes × 1 half life ÷ 10 minutes
= 5 half lives
Balance the equation ___ CaCO3 -> ____ CaO + ____ CO2
Answer:
CaCO3 -> CaO + CO2
Explanation:
Woahhhh, did you balance it yourself just then?
Consider the following data on some weak acids and weak bases
acid
Ka
name formula
acetic acid
HCH3CO2
1.8 x10−5
hydrocyanic acid
HCN
4.9 x 10−10
base
Kb
name formula
pyridine
C5H5N
1.7 x 10−9
ammonia
NH3
1.8 x 10−5
Use this data to rank the following solutions in order of increasing pH. In other words, select a '1' next to the solution that will have the lowest pH, a '2' next to the solution that will have the next lowest pH, and so on.
a. 0.1M NaCH3CO2
b. 0.1M NH4Br
c. 0.1M NaBr
d. 0.1M KCN
Answer:
b < c < a < d
Explanation:
The weak acid with the lowest pKa will be the most acidic. In the other way, the conjugate base which the acid is weak will be strong.
The weak base with the lowest pKb will be the most basic. And the conjugate base of the weak base will be a strong acid.
Ka Acetic acid = 1.8x10-5
Ka HCN = 1.9x10-10
Kb pyridine = 1.7x10-9
Kb NH3 = 1.8x10-5
NH4Br is the conjugate base of a weak base. That means is a strong acid.
NH4Br has the lowest pH
NaBr is the conjugate base of a strong acid, HBr. That means NaBr is neutral
The most basic between the conjugate base of the acetic acid, NaCH3CO2 and KCN is KCN because the acetic acid is the stronger acid regard to HCN.
The rank is:
NH4Br < NaBr < NaCH3CO2 < KCN
b < c < a < dIf the mass defect for a radionuclide is –8.7839×10-30 kg, what's the binding energy per atom?
Question 7 options:
A)
–7.8944×10-13 J/atom
B)
–4.76×1011 J/atom
C)
–7.8944×10-13 kJ/atom
D)
7.8944×10-13 J/atom
Answer:
A) –7.8944×10-13 J/atom
Explanation:
Mass defect of a radionuclide (m)
[tex]=-8.7839[/tex]×[tex]10^{-30} kg[/tex]
Formula for binding energy
[tex]E=mc^{2}[/tex]
[tex]=(-8.7839x10^{-30} kg)(3x10^{8} m/s)^{2}[/tex]
[tex]E=-7.8944x10^{-13} J/atom[/tex]
If the mass defect for a radionuclide is – 8.7839 × 10⁻³° kg, the binding energy per atom will be –7.8944 × 10⁻¹³ J/atom. The correct option is A.
What is radionuclide?A radionuclide is an unstable nuclide because it contains so much charge. The excess energy is used by the gamma radiation by the nucleus, the electron uses energy to move to another orbital.
Radionuclides are particles that are used to scanning or monitor the radioactive chemicals that are in the body due to swallowing or inhaling.
The binding energy per atom can be calculated by the formula
The mass of defect of a radionuclide (m) is – 8.7839 × 10⁻³° kg
E = mc²
E = – 8.7839 × 10⁻³° x 3 x 10⁸ m/s
E = –7.8944 × 10⁻¹³ J/atom.
Thus, the correct option is A. –7.8944×10-13 J/atom.
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Write the balanced equation for the equilibrium reaction for the dissociation ofsilver chloride in water, and write the K expression for this reaction. Then create an ICE chart. Since we know the equilibrium concentration of the silver ion, we can solve for Ksp.Does it agree with the literature value
Answer:
See explanation
Explanation:
Hello there!
In this case, since the the concentrations are not given, and not even the Ksp, we can solve this problem by setting up the chemical equation, the equilibrium constant expression and the ICE table only:
[tex]AgCl(s)\rightleftharpoons Ag^+(aq)+Cl^-(aq)[/tex]
Next, the equilibrium expression according to the produced aqueous species as the solid silver chloride is not involved in there:
[tex]Ksp=[Ag^+][Cl^-][/tex]
And therefore, the ICE table, in which x stands for the molar solubility of the silver chloride:
[tex]\ \ \ \ \ \ \ \ \ \ \ \ \ \ AgCl(s)\rightleftharpoons Ag^+(aq)+Cl^-(aq)[/tex]
I - 0 0
C - +x +x
E - x x
Which leads to the following modified equilibrium expression:
[tex]Ksp=x^2[/tex]
Unfortunately, values were not given, and they cannot be arbitrarily assigned or assumed.
Regards!
PLZ HELP "NO LINKS"
A vessel of volume 22.4 dm3 contains 2.0 mol H2(g) and 1.0 mol N2(g) at 273.15 K.
(a) Calculate the mole fractions of each component.
H2:
N2:
(b) Calculate the partial pressures of each component.
H2:
N2:
(c) Calculate the total pressure.
Thanks!
Answer: (a) Mole fraction of [tex]H_{2}[/tex] is 0.66.
Mole fraction of [tex]N_{2}[/tex] is 0.33
(b) The partial pressure of [tex]H_{2}[/tex] is 1.98 atm.
The partial pressure of [tex]N_{2}[/tex] is 0.99 atm.
(c) The total pressure is 3.0 atm
Explanation:
Given: Volume = [tex]22.4 dm^{3}[/tex] (1 [tex]dm^{3}[/tex] = 1 L) = 22.4 L
Moles of [tex]H_{2}[/tex] = 2.0 mol
Moles of [tex]N_{2}[/tex] = 1.0 mol
Total moles = (2.0 + 1.0) mol = 3.0 mol
Temperature = 273.15 K
Now, using ideal gas equation the total pressure is calculated as follows.[tex]PV = nRT\\[/tex]
where,
P = pressure
V = volume
n = number of moles
R = gas constant = 0.0821 L atm/mol K
T = temperature
Substitute the values into above formula as follows.
[tex]PV = nRT\\P \times 22.4 L = 3.0 mol \times 0.0821 L atm/mol K \times 273.15 K\\P = 3.0 atm[/tex]
The mole fractions of each component:The mole fraction of [tex]H_{2}[/tex] is calculated as follows.
[tex]Mole fraction = \frac{moles of H_{2}}{moles of H_{2} + moles of N_{2}}\\= \frac{2.0 mol}{(2.0 + 1.0) mol}\\= 0.66[/tex]
The mole fraction of [tex]N_{2}[/tex] is as follows.
[tex]Mole fraction = \frac{moles of N_{2}}{moles of H_{2} + moles of N_{2}}\\= \frac{1.0 mol}{(2.0 + 1.0) mol}\\= 0.33[/tex]
The partial pressures of each component:Partial pressure of [tex]H_{2}[/tex] are as follows.
[tex]P_{H_{2}} = P_{total} \times mole fraction of H_{2}\\= 3.0 atm \times 0.66\\= 1.98 atm[/tex]
Partial pressure of [tex]N_{2}[/tex] are as follows.
[tex]P_{N_{2}} = P_{total} \times mola fraction of N_{2}\\= 3.0 atm \times 0.33\\= 0.99 atm[/tex]
how a scientist might use a graph of the
relationship between population growth and time to identify
a trend
You and several novice researchers decide to set up some experiments in an attempt to explain why potassium reacts with oxygen to form a superoxide. One of your team members proposes that potassium's capacity to form a superoxide compound is related to a low value for the first ionization energy. If you wanted to validate this hypothesis, indicate two metals other than potassium (in order of increasing atomic number) that you could examine to see if they also form superoxides when reacted with oxygen gas.
Required:
Express your answers as chemical symbols separated by a comma.
Answer:
Rubidium and cesium
Explanation:
It is noteworthy to say here that larger cations have more stable superoxides. This goes a long way to show that large cations are stabilized by large cations.
Let us consider the main point of the question. We are told in the question that the reason why potassium reacts with oxygen to form a superoxide is because of its low value of first ionization energy.
The implication of this is that, the other two metals that can be examined to prove this point must have lower first ionization energy than potassium. Potassium has a first ionization energy of 419 KJmol-1, rubidium has a first ionization energy of 403 KJ mol-1 and ceasium has a first ionization energy of 376 KJmol-1.
Hence, if we want to validate the hypothesis that potassium's capacity to form a superoxide compound is related to a low value for the first ionization energy, we must also consider the elements rubidium and cesium whose first ionization energies are lower than that of potassium.
give same examples of ways that people destroy the plant animals relationship?
Match the element with its oxidation number (charge).
1. +1 O
2. -1 Ca
3. -3 Si
4. -2 Al
5. +2 N
6. +3 Na
7. +/- 4 F
Answer:
The answer is in the problem
Explanation:
As general rule of number of oxygen is -2:
O → -2
Alkali metals (Li, Na, K) are always +1
Na → +1
Alkali earth methals (Be, Mg, Ca...) are always +2
Ca → +2
The halogen group (F, Cl, Br...) is always -1
F → -1
The oxidation number of Si (+/- 4)
Aluminium is, usually +3
And to complete the octet rule in nitrogen, 3 electrons are required. That means:
N → -3
un MODELO ATÓMICO es:
a. Una esfera con partículas positivas y negativas
b. La estructura mínima de la materia.
c. Una serie de descubrimientos.
d. La representación de un átomo donde se explica su comportamiento y características.
Answer:
Creo que es D pero no tan segura
Explanation:
Which of the following statements about energy is FALSE?
A. Energy can be converted from one type to another.
B. The total energy of a system remains constant.
C. Energy is the capacity to do work.
D. Kinetic energy is the energy associated with its position or composition
E. Systems tend to change in order to lower their potential energy
According to law of conservation of energy, the statement which is false is kinetic energy is the energy associated with its position or composition.
According to law of conservation of energy, it is evident that energy is neither created nor destroyed rather it is restored at the end of a chemical reaction .
Law of conservation of mass and energy are related as mass and energy are directly proportional which is indicated by the equation E=mc².Concept of conservation of mass is widely used in field of chemistry, fluid dynamics.
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HELP PLISSS !!!!! what did a criminal often use to poison? A. Eye medication. B. potassium cyanide
Answer:
potassium cyanide
Explanation:
while eye medications do harm your immune system it is not enough to kill someone. criminals mainly used potassium cyanide because it was cheap. it serves as a substitute for ethanol.
HC2HO3(aq)+H2O(l)⇄H3O+(aq)+C2HO3−(aq)
pKa=3.18
at 25°C
The equilibrium for the acid ionization of HC2HO3 is represented by the equation above. If 10.0mL of 0.20MHC2HO3 reacts with 5.0mL of 0.10MNaOH, which of the following could be used to calculate the correct pH of the resulting solution?
A) pH=pKa+log(0.100.20)
B) pH=pKa+log(0.0050×0.100.0100×0.20)
C) pH=pKa+log[((0.0050×0.10)0.0150)/((0.0100×0.20)−(0.0050×0.10)0.0150)]
D) pH=pKa+log[((0.0050×0.10)+(0.0100×0.20)0.0150)/((0.0100×0.20)−(0.0050×0.10)0.0150)]
Answer:
C) pH=pKa+log[((0.0050×0.10)0.0150)/((0.0100×0.20)−(0.0050×0.10)0.0150)]
Explanation:
To find the pH of a buffer (The mixture of the weak acid and its conjugate base) we have to use Henderson-Hasselbalch equation:
pH = pKa + log [Base] / [Acid]
Where pKa is the pka of the buffer and [] is molar concentration of the species of the buffer
The [Base] is equal to the concentration of NaOH added:
0.10M * (0.005L / 0.015L)
And the concentration of the acid [Acid] is the initial concentration of the acid - the concentration of the NaOH added:
0.0100L * (0.20M)/0.0150L - 0.10M * (0.005L / 0.015L)
That means the pH of the buffer is:
C) pH=pKa+log[((0.0050×0.10)0.0150)/((0.0100×0.20)−(0.0050×0.10)0.0150)]
Answer:
C) pH=pKa+log[((0.0050×0.10)0.0150)/((0.0100×0.20)−(0.0050×0.10)0.0150)]
Explanation:
The equilibrium for the acid ionization of HC2HO3 is represented by the equation above. If 10.0mL of 0.20MHC2HO3 reacts with 5.0mL of 0.10MNaOH, which of the following could be used to calculate the correct pH of the resulting solution. pH=pKa+log[((0.0050×0.10)0.0150)/((0.0100×0.20)−(0.0050×0.10)0.0150)]
What is the molarity of a solution that contains 0.220 moles KOH in 0.350 L of solution?
Answer:
0.628 M.
Explanation:
In order to solve this problem we need to keep in mind the definition of molarity:
Molarity = moles / litersWe are given both the number of moles and the volume of solution, meaning we can now proceed to calculate the molarity:
Molarity = 0.220 mol / 0.350 LMolarity = 0.628 Mwhat element in magma is most abundant
Answer:
Oxygen and Silicon
Explanation:
Oxygen and Silicon are the most abundant elements in magma, SiO₂
-TheUnknownScientist
Which of the following contains the highest number of electrons?
OA) hydroxide ion
OB) oxonium ion
C) ammonium ion
OD) oxide ion
O E) all of them contains the same number of electrons
what is the difference between transmutation and natural radioactivity
Determine the number of electrons in an Cl ion with a charge of -3
Answer:
There are 20 electrons.
Explanation:
Chlorine has 17 electrons in its atom to begin with (you can tell from the proton number in the periodic table).
A charge of -3 means that the chlorine atom gained 3 electrons, and now needs to lose 3 electrons to return to its atom configuration.
Which of the two Lewis/electron dot structure representations, which is
the correct one for oxygen gas? PICTURE BELOW
Answer:
A
Explanation:
What is the correct definition of temperature
Answer:
i'm pretty sure its the last answer and if not its the 2nd one
If 6.75 g of NaOH are dissolved in 50.00 g of water and the temperature increases
from 20.5°C to 47.8 °C.
a. Is this an example of an endothermic or exothermic reaction?
b. What is the q for the reaction? (Remember since the NaOH dissolves in water add the
masses to get the m)
C. How many moles of NaOH are dissolved?
d. What is the AH for the reaction?
Answer: THE STANDARD HEAT OF SOLUTION OF SODIUM HYDROXIDE IN WATER IS -7.68 KJ PER MOLE.
A generator makes electricity from _____.
chemical reactions
kinetic energy
heat
friction
You are performing an acid-base neutralization reaction in the laboratory to determine the concentration of an unknown base. You are supposed to titrate it with a monoprotic acid, but your lab partner accidentally fills your buret with sulfuric acid, a diprotic acid, with the same concentration as the acid called for in the experiment. How will the volume of diprotic acid compare to the volume of monoprotic acid you would have used
Answer:
Volume is reduced to half
Explanation:
Acid base titration are commonly used reactions in a lab, and are ofter used to get pH or different kind of solutions.
The neutralization of an acid base reaction is reached, when the solution (having added an indicator previously) changes its original color. chemically speaking, this occurs when the number of moles of the acid and the base are balanced and equal. In other words the following:
n₁ = n₂ (1)
This expression can also be expressed in function of concentration and volume:
M₁V₁ = M₂V₂ (2)
From here, solving for V₁:
V₁ = M₂V₂ / M₁
Now, this expression is true only when we have the same kind of substance that can lose or gain the same number of hydrogens.
Lets suppose that we have as base NaOH (Monoprotic base) and HCl (monoprotic acid), the titration reaction would be:
NaOH + HCl --------> NaCl + H₂O
As both of the species are monoprotic, the number of moles are the same when they reach the equilibrium, so, expression (2) can be used, and calculate volume or concentrations.
However, in this case, a partner made a mistake and use a diprotic acid, in this case, H₂SO₄, In this case, things chance because H₂SO₄ is diprotic, meaning that we need to dissociate two hydrogens in equilibrium, therefore, expression (2) would be something like this.
Acid: 1; Base: 2
H₂SO₄ + 2NaOH ------> Na₂SO₄ + H₂O
nH₂SO₄ = n₁ = 1
nNaOH = n₂ = 2
n₁/n₂ = 1/2
2n₁ = n₂ (3)
Writting this, in function of concentration and volume, it would be:
2M₁V₁ = M₂V₂ (4)
From here, if we solve for the volume of the acid (V₁):
V₁ = M₂V₂ / 2M₁
Therefore, according to this expression, we can see that the volume required of the acid would be half the volume required of the monoprotic acid. For example, if we need 50 mL of Chloridic acid to reach the equivalence point with NaOH, then, with H₂SO₄ it will only need 25 mL. This, of course, assuming that concentrations are the same, and volume of the base used, the same.
Hope this helps
When H2(g) reacts with F2(g) to form HF(g) , 542 kJ of energy are evolved for each mole of H2(g) that reacts. Write a balanced thermochemical equation for the reaction with an energy term in kJ as part of the equation.
Answer:
H₂(g) + F₂(g) ⇒ 2 HF(g) ΔH°rxn = -542 kJ
Explanation:
Let's consider the unbalanced equation that occcurs when H₂(g) reacts with F₂(g) to form HF(g).
H₂(g) + F₂(g) ⇒ HF(g)
In order to get the balanced equation, we will multiply HF(g) by 2.
H₂(g) + F₂(g) ⇒ 2 HF(g)
To convert a balanced equation into a thermochemical equation, we need to add the standard enthaply of the reaction, considering that 542 kJ of energy are evolved for each mole of H₂(g) and there is 1 mole of H₂(g) in the balanced equation. By convention, when energy is released, it takes a negative sign. The thermochemical equation is:
H₂(g) + F₂(g) ⇒ 2 HF(g) ΔH°rxn = -542 kJ
Write a balanced equation for the double-replacement precipitation reaction described, using the smallest possible integer coefficients. A precipitate forms when aqueous solutions of nickel(II) nitrate and sodium carbonate are combined. Do not include states such as (s) or (aq). It is not necessary for you to indicate which of the products is the precipitate.
Answer:
Ni(NO₃)₂ + Na₂CO₃ ⇒ NiCO₃ + 2 NaNO₃
Explanation:
Let's consider the unbalanced equation for the reaction that occurs when aqueous solutions of nickel(II) nitrate and sodium carbonate are combined. This is a double-replacement precipitation reaction.
Ni(NO₃)₂ + Na₂CO₃ ⇒ NiCO₃ + NaNO₃
We will balance the equation using the trial and error method.
First, we will balance Na atoms by multiplying NaNO₃ by 2.
Ni(NO₃)₂ + Na₂CO₃ ⇒ NiCO₃ + 2 NaNO₃
As we can see, the equation is balanced.
Are sperm and egg cells exact copies of the plant cell
Answer:
No
Explanation:
thats scientifically impossible
How many hydrogen molecules are in h2
Answer:
two
Explanation:
The symbol “H” means the hydrogen atom; “2H” means two hydrogen atoms that do not make a molecule: they are just two separate (individual) atoms; “H2” means the hydrogen molecule (two hydrogen atoms that came together, sharing their electrons); “2H2” means two separate hydrogen molecules.
3. Determine the moles of sodium, Na, containing 7.9x1024 atoms.
Answer:
12.7mol Na.
Explanation:
Hello there!
In this case, according to the concept of mole, which stands for the amount of substance, we can recall the concept of Avogadro's number whereby we understand that one mole of any substance contains 6.022x10²³ particles, for the given atoms of sodium, we can calculate the moles as shown below:
[tex]7.9x10^{23}atoms*\frac{1mol}{6.022x10^{23}atoms} \\\\[/tex]
Thus, by performing the division we obtain:
[tex]12.7molNa[/tex]
Regards!
Potassium nitrate, KNO3 , has a molar mass of 101.1 g/mol. In a constant-pressure calorimeter, 13.3 g of KNO3 is dissolved in 213 g of water at 23.00 °C . KNO3(s)−→−−H2OK+(aq)+NO−3(aq) The temperature of the resulting solution decreases to 19.60 °X . Assume that the resulting solution has the same specific heat as water, 4.184 J/(g·°C) , and that there is negligible heat loss to the surroundings. How much heat was released by the solution
Answer:
[tex]Q_{sln}=-3219.25 J[/tex]
Explanation:
Hello there!
In this case, for this calorimetry problem, it is possible for us to infer that the heat of the reaction of dissolution of KNO3 is absorbed by the solution composed by the former and water so that we can write:
[tex]Q_{rxn}=-Q_{sln}[/tex]
Thus, given the mass, specific heat and temperature of the solution, we plug in the data to obtain the heat absorbed, by the reaction:
[tex]Q_{rxn}=-m_{sln}C_{sln}\Delta T _{sln}\\\\Q_{rxn}=-(13.3+213)g(4.184\frac{J}{yg\°C} )(19.60-23.00)\°C\\\\Q_{rxn}=3219.25J[/tex]
Also, we can say the the heat released by the solution was -3219.25 J.
Best regards!
The x-intercept shows us where the temperature can be no lower, defined as absolute zero. Absolute zero is 0 K. Look at the graph.
Did the line reach (0,0)? If not, how close to absolute zero was the line?
Answer:
someone please answer!:(
Answer:
No, it was 130k way from (0,0).
Explanation: