The question is incomplete, the complete question is;
The half-life of strontium-90 is about 29 years. How many half-lives have elapsed when 6.25% of a strontium- 90 sample remains in the container?
Answer:
4 half lives
Explanation:
From;
N/No = (1/2)^t/t1/2
N= amount of strontium-90 present at time t
No= amount of strontium-90 originally present
t= time taken
t1/2 = half life of strontium-90
But N= 0.0625No
Hence;
0.0625No/No = (1/2)^t/29
0.0625 = (1/2)^t/29
(1/2)^4 = (1/2)^t/29
4 = t/29
t = 4 × 29
t= 116 years
Hence four half lives have elapsed
Cells can regulate different processes in two ways. They can turn on and off the genes that make enzymes, or they can
A)
increase the activation energy of a reaction.
B)
increase the amount of energy needed to carry out the preferred process.
C)
regulate the enzymes that are already made.
D)
decrease the amount of energy needed to carry out the preferred process.
Answer:
im pretty sure its d
Explanation:
If 45 mL of a 6 M solution is diluted to a final volume of 250 mL, what is concentration of the final solution?
Answer:
1.08 M
Explanation:
From the question given above, the following data were obtained:
Initial volume (V₁) = 45 mL
Initial concentration (C₁) = 6 M
Final volume (V₂) = 250 mL
Final concentration (C₂) =?
The final concentration of the solution can be obtained by using the dilution formula as illustrated below:
C₁V₁ = C₂V₂
6 × 45 = C₂ × 250
270 = C₂ × 250
Divide both side by 250
C₂ = 270 / 250
C₂ = 1.08 M
Therefore, the final concentration of the solution is 1.08 M.
20 POINTS!!
What is the enthalpy of combustion when 1 mol C6H6(g) completely reacts with oxygen?
2C6H6(g) + 15O2(g) ? 12CO2(g) + 6H2O(g)
Options:
A. - 6339 kJ/mol
B. - 3169 kJ/mol
C. 1268 kJ/mol
D. 6339 KJ/mol
Answer:
-3169
Explanation:
trust the process
-3169 kJ/mol is the enthalpy of combustion when 1 mol [tex]C_6H_6(g)[/tex] completely reacts with oxygen.
Explanation:
Given:
The reaction of combustion of [tex]C_6H_6(g)[/tex] along with enthalpies of formation of the compounds.
To find:
The enthalpy of combustion when 1 mol [tex]C_6H_6(g)[/tex] completely reacts with oxygen.
Solution:
[tex]2C_6H_6(g) + 15O_2(g) \rightarrow 12CO_2(g) + 6H_2O(g)[/tex]
Enthalpy of the reaction:
[tex]\Delta H^o_{rxn}=\sum [\Delta H^o_{f,products}]-\sum [\Delta H^o_{f,reactants}]\\=[12mol\times \Delta H^o_{f.CO_2(g)}+6mol\times \Delta H^o_{f,H_2O(g)}]-[2 mol\times \Delta H^o_{f.C_6H_6(g)}+15\times \Delta H^o_{f,O_2(g)}]\\=[12mol\times (-393.50 kJ/mol)+6mol\times (-241.82 kJ/mol)]-[2mol\times 82.90kJ/mol+15mol\times 0 kJ/mol]\\=-6338.72 kJ[/tex]
[tex]2C_6H_6(g) + 15O_2(g) \rightarrow 12CO_2(g) + 6H_2O(g).\Delta H^o_{rxn}=-6338.72 kJ[/tex]
When 1 mole of [tex]C_6H_6(g)[/tex] reacts with oxygen gas:
[tex]=\frac{\Delta H^o_{rxn}}{\text{2 mol of } C_6H_6}\\=\frac{-6338.72 kJ}{2 mol}\\=-3169.36 kJ/mol\approx -3169 kJ/mol[/tex]
-3169 kJ/mol is the enthalpy of combustion when 1 mol [tex]C_6H_6(g)[/tex] completely reacts with oxygen.
Learn more about enthalpy of combustion here:
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Need help asap please!
Which contributes to the polarity of a water molecule?
A. a linear shape along with strong covalent bonds
B. deflection of hydrogen atoms by lone pairs of electrons
C. no difference in the electronegativity of oxygen and hydrogen
D. hydrogen bond formation between water molecules
Answer:
B
Explanation:
because polarity of the water molecules is due to the B. deflection of the hydrogen atoms by the lone pair of electrons.
Answer:
B
Explanation:
This graph represents a population of molecules in a gas versus the distribution of the average velocity(speed) of its molecules in that population. Assume all molecules to be of the same mass. In reading the graph, it is important to note three things. One, is the most probable speed is at the peak of the curve. Secondly, the most probable speed increases as the temperature increases (so shift to the right), and the distribution broadens as it increases.
On the graph, indicate the average kinetic energy of the population.
Explain your answer.
What part of the graph indicates the temperature of the sample?
Explain your answer.
Sketch a curve that represents the distribution of molecules at a temperature below the one shown. Label it as T2. Describe both T and T2 in terms of their average kinetic energy. Be specific and detailed.
Submit your answer below.
Answer:
Part A
Given that the graph is symmetrical and bell shaped, the average kinetic energy is given by the midline of graph, which corresponds to the common speed of the highest number of the population
Part B
The formula for the average kinetic energy, K.E. = (3/2)·(R/NA)·T
Therefore, the part of the graph that indicates the temperature of the sample is the average kinetic energy. K.E.
Part C
At a lower temperature, the heat is less evenly distributed and we have the distribution T2 higher than T1
Please see the attached graph created with MS Visio
Explanation:
what do u mean by change in state of matter?define it.
Answer:
The mode of changing from one state of matter into another state and back to the former or original state is called change in state of matter .
hope it is helpful to you
Answer:
change in one state from another and back in its own original is known as change in state of matter
What are the two factors that affect that density of matter ?
Mass and volume are two factors that affect that density of matter!
Ethanol has a heat capacity of 2.46 Jig 'c. If 50 g of ethanol has a temperature of 30°C and a piece of hot Copper is added to the ethanol causing the
temperature to increase to 70°C. What is the amount of heat absorbed by the ethanol?
Explanation:
there it is fella tried on ma own consciousness
HELPPP 50 POINTS
How are the things people are
doing helpful to them and harmful to them?
when potassium chloride is dissolved in water *
a)heat is given off
b)heat is taken in
c)temperature stays same
Answer:
Option B . heat is taken in
Answer:
B
Explanation:
we need to eat,drink,and sleep to be healthy
PLEASE HELP QUICK
The graph shows the distribution of energy in the particles of two gas samples at different temperatures, T1 and T2. A, B, and C represent individual particles.
Based on the graph, which of the following statements is likely to be true? (3 points)
Particle A is more likely to participate in the reaction than particle B.
Particle C is more likely to participate in the reaction than particle B.
The number of particles able to undergo a chemical reaction is less than the number that is not able to.
More gas particles participate in the reaction at T2 than at T1.
Answer:
Okay, I think I may actually have an answer for you. I would go with C, "The number of particles able to undergo a chemical reaction is less than the number that is not able to."
Explanation:
I just took a quiz with a similar question, and B is the only gas particle that is able to react. This cancels out all the other answers, as A and B are obviously incorrect based on that information, and it rules out D because T1 is the only sample with a particle able to react. I hope this helps!
Answer:
C is the right answer
Explanation:
Why don’t scientists use the Bohr model above to explain charge transfer?
Answer:
nsksbsjensnsjeiejensbsksks
Calculate the pressure kPa of 0.421 mole of helium gas at 254 degree celsius when it occupies a volume of 3.32 L.
How much water can be produced when 18 grams of pentane is burned in air? C5H12 + 8 02 --> 5 CO2 + 6 H2O. 9.0 g 18 g 27 g 36 g 729
Answer: The mass of water produced is 27 g
Explanation:
The number of moles is defined as the ratio of the mass of a substance to its molar mass.
The equation used is:
[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex] ......(1)
Given mass of pentane = 18 g
Molar mass of pentane = 72.15 g/mol
Plugging values in equation 1:
[tex]\text{Moles of pentane}=\frac{18g}{72.15g/mol}=0.250 mol[/tex]
The given chemical equation follows:
[tex]C_5H_{12}+8O_2\rightarrow 5CO_2+6H_2O[/tex]
By the stoichiometry of the reaction:
If 1 mole of pentane produces 6 moles of water
So, 0.250 moles of pentane will produce = [tex]\frac{6}{1}\times 0.250=1.5mol[/tex] of water
Molar mass of water = 18 g/mol
Plugging values in equation 1:
[tex]\text{Mass of water}=(1.5mol\times 18g/mol)=27g[/tex]
Hence, the mass of water produced is 27 g
Is distilled water pure or impure
Answer:
pure
Explanation:
Distilled water is a form of pure water, hence it is not bad or harmful to drink distilled water.
Answer:
I think it's pure. hope this helps◉‿◉
A doctor is testing a new medication and he doesn’t tell the people in the study about the possible side effects of the medicine. He is _____.
What is nitrogen?? explain!!
Answer:
Nitrogen is a naturally occurring element that is essential for growth and reproduction in both plants and animals. It is found in amino acids that make up proteins, in nucleic acids, that comprise the hereditary material and life's blueprint for all cells, and in many other organic and inorganic compounds.Explanation:
Nitrogen is a naturally occuring element that is essential for growth and reproduction in both plants and animals.Hope it's help you~✌️✌️PLEASE HELP ME PLEASE PLEASE NOW
Answer:
the amount of trials in an experiment
1
A coil of wire with an iron inside
becomes an? when there is
current.
Enter your answer
Answer:
A magnet
Explanation:
What is the compound name of NO3?
Answer:
NITRATE ION
Explanation:
How much liquid is needed to prepare 629.1mL of a solution that has a new concentration of 11.2M if the stock solution is 26.1M
Answer:
270. mL
General Formulas and Concepts:
Acid-Base Titrations
Dilution: M₁V₁ = M₂V₂
M₁ is stock molarityV₁ is stock volumeM₂ is new molarityV₂ is new volumeExplanation:
Step 1: Define
Identify
[Given] V₂ = 629.1 mL
[Given] M₂ = 11.2 M
[Given] M₁ = 26.1 M
[Solve] V₁
Step 2: Find Stock Volume
Substitute in variables [Dilution]: (26.1 M)V₁ = (11.2 M)(629.1 mL)Multiply: (26.1 M)V₁ = 7045.92 M · mLIsolate V₁ [Cancel out units]: V₁ = 269.959 mLStep 3: Check
Follow sig fig rules and round. We are given 3 sig figs as our lowest.
269.959 mL ≈ 270. mL
Which organisms release carbon dioxide into the air (abiotic matter) in an ecosystem?
only producers
only decomposers
only consumers
producers, consumers, and decomposers
Answer:
All 3
Explanation:
Decomposers break apart complex organic materials into more elementary substances: water and carbon dioxide, plus simple compounds containing nitrogen, phosphorus, and calcium. All of these components are substances that plants need to grow.
Some decomposers are specialized and break down only a certain kind of dead organism. Others are generalists that feed on lots of different materials. Thanks to decomposers, nutrients get added back to the soil or water, so the producers can use them to grow and reproduce.
Fossil fuels are considered to be:
a.
irreplaceable resources
c.
renewable resources
b.
nonrenewable resources
d.
hazardous wastes
Please select the best answer from the choices provided
A
B
C
D
A solution has a [H3O+] of 1 × 10−3 M. What is the [OH−] of the solution?
A. 11 M
B. 14 M
C. 1 × 10−14 M
D. 1 × 10−11 M
Answer:
D. 1x10⁻¹¹ M
Explanation:
For any given aqueous solution the following formula is true:
1x10⁻¹⁴ = [H₃O⁺] * [OH⁻]
1x10⁻¹⁴ is the ion-product constant of water, Kw.
We input the given value of [H₃O⁺]:
1x10⁻¹⁴ = 1x10⁻³ * [OH⁻]
And solve for [OH⁻]:
[OH⁻] = 1x10⁻¹¹ M
Thus the correct answer is option D. 1x10⁻¹¹ M.
Answer:
D. 1x10⁻¹¹ M
Explanation:
I took the test :)
2) Two students are running in a cross country race. One has a mass of 60 kg, while the other has a mass of 70 kg. If they are both running with a speed of 7 m/s, which has more momentum? Why?
Answer:
The second student with mass 70kg has more momentum
Explanation:
Using the formula:
p = m × v
Where;
p = momentum (kgm/s)
m = mass (kg)
v = velocity (m/s)
According to this question, two students are running in a cross country race.
Student 1 has the following; m = 60kg, v = 7m/s
Student 2 has the following; m = 70kg, v = 7m/s
Using p = mv
Student 1, p = 60 × 7 = 420 kgm/s
Student 2, p = 70 × 7 = 490 kgm/s
From the result of the above calculations, student 2 with mass 70kg has more momentum.
relate the intermolecular forces in hydrocarbons to their physical properties and uses
The physical properties of alkenes and alkynes are generally similar to those of alkanes or cycloalkanes with equal numbers of carbon atoms. Alkynes have higher boiling points than alkanes or alkenes, because the electric field of an alkyne, with its increased number of weakly held π electrons, is more easily distorted, producing stronger attractive forces between molecules.
Need answer ASAP!!!!
Select the correct answer.
What happens to sodium chloride when it dissolves in water?
© A. Electrons are transferred from sodium atoms to chlorine atoms, forming positive and negative ions.
O B.
Each sodium ion pairs with a chloride ion, and the pair of ions is surrounded by water molecules.
C.
The water molecules attract both the sodium ions and the chloride ions, pulling them together.
© D.
The sodium ions are separated from the chloride ions, and both dissolve separately into the water.
Answer:
I am sure it is D or C. have a nice day
Which will boil faster distilled water or salt water and why?
Answer:
The distilled water will be boiled faster as it does not contain any non - volatile solute.
- The salty water contains different non - volatile salts in it.
- Due to the presence of these salts, its vapour pressure will be decreased and boiling point will be elevated.
- So, salty water will take more time to boil.
- On the other hand, distilled water does not have any such solute and due to this its vapour pressure will not be affected.
- Hence, it will boil fast than salty water.
(04.04 LC)
During light-dependent reactions, carbon dioxide is converted to glucose.
True
O False
Answer:
false
Explanation:
it happens in light-independent reactions
There is a close relation between forest
and wildlife.
Answer:
habitat
Explanation:
wild animal need