A 60-g sample of radioactive isotope is measured after two half-lives have passed. What pair of percentages describes the sample after two half-lives?.

Answers

Answer 1

Answer:

25% is left   15 gm

Explanation:

(1/2)^2 = 25%

Answer 2

Answer:

b. 25% unchanged and 75% stable

Explanation:

got it right on edge


Related Questions

What is the substance that is dissolved in a solution?
A)solvent
B)solute
C) mixture
D) electrolyte

Answers

Answer:

solute dissolves in a solution

Answer:

solvent

Explanation:

because solvent are liquid that disolves

Look at the products of the chemical reaction to determine if the reactant added to water caused an acid reaction, a base reaction, or a neutralization reaction.


Acid


Neutralization


Base

1.
2HF + 2CaOH -> 2H2O + 2NaF

2.
3HI + 2H2O -> 2H3O+ + 3I- + H+

3.
2CH3COO- + H2O -> CH3COO- + OH- + CH3COOH

0.05 moles of HCL are added to 2 L of H2O. What is the molarity of the solution?

Impossible to answer the question with the information provided.


1.60


0.025M


10.4

Answers

1. The reaction is a neutralization reaction

2. The reactant added to the water causes an acid reaction

3. The reactant added to the water causes a base reaction

4. The molarity of the solution is 0.025 M

What is a neutralization reaction?

This is a reaction involving an acid and a base which result in the formation of salt and water only

HF + NaOH –> H₂O + NaF

The reaction above indicates neutralization since the reaction produces water (H₂O) and salt (NaF) only

What is an acid?

An acid is a substance which dissolves in water to produce hydronium ion H₃O⁺

3HI + 2H₂O —> 2H₃O⁺ + 3I¯ + H⁺

The reaction above is an acid reaction since it produces H₃O⁺

What is a base?

A base is a substance which dissolves in water to produce hydroxide ion OH¯

2CH₃COO¯ + H₂O —> CH₃COO¯ + OH¯ + CH₃COOH

The reaction above is a base reaction since OH¯ is produced.

How to determine the molarity Mole = 0.05 mole Volume = 2 LMolarity =?

Molarity = mole / Volume

Molarity = 0.05 / 2

Molarity = 0.025 M

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What is the difference between an endothermic and an exothermic reaction?

Answers

An exothermic process releases heat, causing the temperature of the immediate surroundings to rise. An endothermic process absorbs heat and cools the surroundings

The acid dissociation constant of alloxanic acid is. Calculate the ph of a solution of alloxanic acid. Round your answer to decimal place

Answers

Answer:

The pH of a 4.4 M solution of boric acid is 4.3

Explanation:

at t=0  cM              0             0

at eqm                    

So dissociation constant will be:

Give c= 4.4 M and  = ?

Putting in the values we get:

Also

Thus pH of a 4.4 M  solution is 4.3

Determine the number of moles of air present in 1.35 l at 750 torr and 17.0°c. ideal gas law formula: pv = nrt(r = 62.396 l•torr/mol•k) which equation should you use? p equals startfraction n r t over v endfraction. n equals startfraction r t over p v endfraction. n equals startfraction p v over r t endfraction.

Answers

The number of moles of air present is 0.056 mole

What is the ideal gas equation?

The ideal gas is one in which molecules do not attract or repel each other.Many gases like oxygen,nitrogen, carbon di oxide can be treated as the ideal gases as particular temperature and pressure.The real gases at high temperature and lower pressure can be treated as ideal gases.

The given data in the question is

Volume = 1.35 L

Pressure (P) = 750 torr

Temperature (T) = 17 °C = 17 + 273 = 290 K

Gas constant (R) = 62.396 L•torr/mol•K

The number of moles (n) =?

How to determine the number of moles:

The number of moles present can be obtained by using the ideal gas equation as illustrated below:

[tex]PV=nRT[/tex]

Divide both sides by RT

[tex]n=\dfrac{PV}{RT}[/tex]

[tex]n=\dfrac{(750\times 1.350}{62.396\times 290)}[/tex]

[tex]n=0.056\ moles[/tex]

Hence, the number of moles of air present is 0.056 mole

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Answer:

answer in picture

Explanation:

For the molecule allene, h2 c = c = ch2, give the hybridization of each carbon atom. Will the hydrogen atoms be in the same plane or perpendicular planes?

Answers

Owing to the fact that allene is not a planar molecule, the hydrogen atoms in the molecule do not lie on the same plane.

What is a plannar molecule?

A planar molecule refers to those molecules that lie on same plane. This means that the atoms in the molecules are all arranged along the same plane.

Now we know that the molecule allene is not a planar molecule. Owing to the fact that allene is not a planar molecule, the hydrogen atoms in the molecule do not lie on the same plane. All the carbon atoms present are sp2 hybridized.

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How can I identify which substance is more thermal stable?

Answers

Thermal stability is the tendency to not break down when exposed to heat. A more negative enthalpy of formation will correlate with more stable products. Therefore, the more negative the enthalpy of formation is for a substance, the greater its thermal stability.

What are two ways continents can grow?

Answers

Answer:

What are three ways continents get bigger?

age of rocks.

fossils.

evidence of melting (subduction)

location on current continents.

glacial deposits.

How should you prepare a buret for titration before loading it with titrant?.

Answers

The buret should be conditioned before loading it with the titrant.

What is a Buret?

This is defined as laboratory apparatus which is used in quantitative chemical analysis to measure the volume of a liquid or a gas.

It should be conditioned with the titrant solution to prevent dilution from occurring as a result of cleaning it with water.

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What is the difference between a reflected and a diffracted sound wave?

Answers

Answer:

Diffraction involves a change in direction of waves as they pass through an opening or around a barrier in their path.

Reflection involves a change in direction of waves when they bounce off a barrier; refraction of waves involves a change in the direction of waves as they pass from one medium to another

Explanation:

If we use water waves as an example, waves hitting shallower water at an angle will slow down and change direction slightly. That is refraction

Waves hitting an island will bend and eventually close in on the "shadow" of the island. That is diffraction

How long do peeled boiled eggs last in the refrigerator?.

Answers

Answer:

approximately 1 week

Explanation:

Hope this helps, feel free to give feedback

1 to 2 weeks but if they smell a litte more stink then usually you better get rid of them or they my make you sick. i got sick for old boiled egg from the school cafeteria a long time ago.

Explanation:

pls explain
help would be appreciated

Answers

Answer:

b

Explanation:

many solids are crystalline hence a is eliminated

graphite contains free electrons while diamond uses all electrons in bonding and many substances have that property hence c is eliminated

only substances made up of carbon produce carbondioxide as the product when burnt

The graph shows the potential energy diagram for an unknown chemical change.


Which chemical change could the graph represent? (1 point)

Group of answer choices

Electrolysis of water

Combustion of iron

Photosynthesis in plants

Adding heat to decompose calcium carbonate

Answers

Based on the energy usage shown by the graph, the best option for the chemical change represented is the combustion of iron.

What chemical change is shown by the graph?

The combustion of iron in oxygen leads to the formation of Iron (III) oxide in solid form.

For the combustion of iron to happen, a lot of heat has to be applied to the iron which is why the potential energy of reactants is high. As the reaction progresses, the energy needed reduces as iron (III) oxide is formed.

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Is food a fuel? Explain your answer. a ?​

Answers

Answer:

no, food is not a fuel because it just give energy to do many activities but it will not provide any fuel only the dead and decaying material which berries under the soil then after a long years it becomes fossil fuel

5.0 g of copper was heated from 20°C to 80°C. How much energy was used to heat Cu? (Specific heat capacity of Cu is 0.38 J/g °C)

Answers

114°

Explanation:

ΔE = mcΔT

ΔE = 5(0.38)(80 - 20)

ΔE = 1.9(60)

ΔE = 114°

Write a paragraph, citing examples from the text, to explain how Dr.
Paul Chirik's process could result in the development of flexible
manufacturing technologies.

Answers

Paul J. Chirik developed methods associated with chemistry catalysis and transition metals, which may result useful for the development of manufacturing technologies.

What is catalysis?

Catalysis refers to the chemical processes that increase the rate of different types of reactions by lowering its activation energy.

Proteins (enzymes) are biological catalysts that increase the rate of chemical reactions in biological systems.

Catalysis may be reached by using transition metals (e.g., actinium and rutherfordium), which result useful in the development of manufacturing technologies.

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Explain in words what is happening in each chemical equation.
nh3 + o2 -> no2- + 3h+ + 2e-
no2- + h2o -> no3- + 2h+ +2e-

Answers

Answer:

Ammonia and oxygen without catalyst | NH3 + O2 → N2 + H2O. With supply of heat, ammonia reacts with oxygen and produce nitrogen gas and water as products. Nitrogen of ammonia is oxidized to nitrogen gas from -3 oxidation state to 0 oxidation state.

Explanation:

When calcium carbonate reacts with hydrochloric acid, calcium ions are transferred to the solution. Write only one net ionic equation for this reaction:

Answers

Answer:

In conclusion, the net ionic equation for the reaction between calcium carbonate and hydrochloric acid is CaCO3 solid plus two H+ aqueous react to form Ca2+ aqueous plus CO2 gas plus H2O liquid.

When calcium carbonate reacts with hydrochloric acid, calcium ions are transferred to the solution, the the net ionic equation is CaCO₃(s) + 2H⁺ → Ca²⁺ + CO₂ + OH⁻ + H⁺.

What is net ionic equation?

Net ionic equation of any reaction is the equation where all entities are written in the form of ions except spectator ions.

Given chemical reaction is:

CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂(g) + H₂O(l)

Ionic reaction for the above reaction will be written as:

CaCO₃(s) + 2H⁺ + 2Cl⁻ → Ca²⁺ + 2Cl⁻ + CO₂ + H⁺ + OH⁻

In the baove reaction Cl⁻ is the spectator ion as they are present on both sides of the given chemical reaction. So the net ionic reaction will be written as:

CaCO₃(s) + 2H⁺ → Ca²⁺ + CO₂ + OH⁻ + H⁺

Hence the net ionic reaction is CaCO₃(s) + 2H⁺ → Ca²⁺ + CO₂ + OH⁻ + H⁺.

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Help me please im stuck

Answers

Answer:

1. mechanical energy

2. Kinetic energy

3. Energy

4. Work

5. potential energy

Explanation:

1. The total amount of mechanical energy is merely the sum of the potential energy and the kinetic energy. This sum is simply referred to as the total mechanical energy 
2. All moving objects have kinetic energy. When an object is in motion, it changes its position by moving in a direction: up, down, forward, or backward.

3. Energy is defined as the ability to cause changes in matter. You can change energy from one form to another when you lift your arm or take a step. In each case, energy is used to move matter — you. The energy of moving matter is called kinetic energy.

4. transfer of energy that occurs when a force makes an object move. For work to occur, an object must move. The motion of the object must be in the same direction as the applied force on the object.

5. potential energy is the energy that is stored in an object due to its position relative to some zero position. An object possesses gravitational potential energy if it is positioned at a height above (or below) the zero height.

A rigid, non-flexible container of O2 gas is being transported to a hospital. What will most likely happen if the vehicle is left unattended and the temperature of the O2 rises?
A. The pressure will increase and the container will leak or explode. B. The pressure will decrease and the container will leak or explode. C. The pressure will increase, but the particles will condense within the container. D. The pressure will decrease and the container will maintain its current temperature.

Answers

If the temperature of the O2 in the container rises as a result of being abandoned for quite some time, the pressure in the container will increase and this may either lead to an explosion or leakage of the gas.

What is the relationship between temperature and pressure of a gas?

At constant volume, the pressure of a gas increases with increased temperature as a result of an increase in the average kinetic energy of the gas molecules which increases the collision rate among the molecules.

Thus, if the temperature of a gas in a container increases, the pressure inside the container will also increase. This may lead to the gas leaking from the container or the container may even outrightly explode due to pressure.

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What is the ph of the solution formed by mixing 25. 0 ml of a 0. 15 m solution of nh3 with 25. 0 ml of 0. 12 m hcl? (kb for nh3 = 1. 8 10–5 )

Answers

Answer:

Explanation:

the answer is 8.66


Mark me brainliest please.

The pH of the solution formed by mixing 25. 0 ml of a 0. 15 m solution of NH₃ with 25. 0 ml of 0. 12 m HCl is 8.66.

What is pH?

pH is potential hydrogen. It is the measurement of the acidity and basicity of any solution.

The solution of NH₃ is 25. 0 ml of a 0. 15 m

The solution of HCl is 25. 0 ml of 0. 12 m hcl

The pkb value is [tex]1.8 \times 10^-^5[/tex]

Putting the value in the formula

[tex]pOH=pKb +log[NH_3][HCl]\\\\ pOH = 1.8 \times 10^-^5+ log \dfrac{25.0 \times 0.15}{ 25.0 \times 0.12} \\\\ pOH = 1.8\times10^-^5+ log1.25 \\\\pOH = 1.8\times 10^-^5 + 1.25 = 3.05\\\\ pH = 14 - pOH = 14 - 1.25 = 8.66[/tex]

Thus, the pH of the solution formed by mixing 25. 0 ml of a 0. 15 m solution of NH₃ with 25. 0 ml of 0. 12 m HCl is 8.66.

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Calculate the number of atoms in 2.1g of nitrogen

Answers

Answer:

2.1×6.02×1023÷ 14

9.03×1022 atom of nitrogen

Explanation:

A tank of oxygen holds 20.0 L at a pressure of 15.0 atm. What is the pressure of this same gas a constant temperature if the oxygen is allowed to expand to 300.0 L?​

Answers

Answer:

khate ko ban randi ko ban

Which of these form electrolytic solutions with water?

Multiple answers.

A) Sodium Chloride (NaCl)

B) Glucose (C6H12O6)

C) Hydrochloric acid (HCl)

D) Carbon Dioxide (CO2)

Answers

Answer:

I believe is the correct answer

Explanation:

a

Clouds form when water vapor ____________ out of the air.

Answers

Answer:

condenses

Explanation:

change or cause to change from a gas or vapor to a liquid.

A chemist creates a reaction between nitrogen and oxygen to form nitrogen monoxide. This reaction is shown by the equation N2(g) + O2(g) ⟶ 2NO(g). The time interval of this reaction is t1 = 12 seconds to t2 = 22 seconds. During this reaction, the O2 concentration changes from 0.237 mol/L to 0.207 mol/L.

What is the average reaction rate for O2 in this reaction?

Answers

Answer: here's the answer to your question

1.3 ×10¹ is the average reaction rate for O[tex]_2[/tex] in this reaction N2(g) + O2(g) ⟶ 2NO(g).

What is rate of reaction?

The pace during which a chemical response takes place is known as the reaction rate and rate of reaction. It is proportional to the rise in product concentration per unit time and the fall in reactant concentration per unit time. Response times can differ wildly.

For instance, cellulose burns in a fire in a matter of seconds as opposed to the sluggish, years-long oxidative corrosion of iron that occurs under Earth's atmosphere. For the majority of reactions, the rate gets slower as it goes along. By tracking the concentration changes over time, one can calculate the pace of a reaction.

concentration of N[tex]_2[/tex] =0.34/0.75=0.45M

concentration of O[tex]_2[/tex] =0.34/0.75=0.45M

concentration of NO=1.2/0.75=1.6

Kc = [NO]²/ [ N[tex]_2[/tex] ] × [ O[tex]_2[/tex] ]

    =  [0.45]²/ [ 0.45 ] × [ 1.6 ]

    = 1.3 ×10¹

Therefore, 1.3 ×10¹ is the reaction rate.

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What does a pH of 13.8 mean

Question 8 options:

The solution is acidic


Impossible to tell from the information provided.


The solution is a strong base


The solution is basic

Answers

A solution with a pH of 13.8 means that the solution is a strong base.

What is pH?

pH refers to power of hydrogen. The pH is a scale used to measure the degree of acidity or alkalinity of a solution.

pH scale ranges from 0 - 14

Where;

0 -6.9 indicates acidic7.1 - 14 indicates basic

However, the closer the pH value is to 1, the more the acidity and vice versa while the closer it is to 14, the more the alkalinity and vice versa.

Therefore, a solution with a pH of 13.8 means that the solution is a strong base.

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2. Which statement is TRUE about ionic compounds?
A. In an ionic compound, the positive ion is the cation, the negative ion is the anion, and the cation
is always named first.
B. In an ionic compound, the positive ion is the cation, the negative ion is the anion, and the anion
is always named first.
C. In an ionic compound, the positive ion is the anion, the negative ion is the cation, and the anion
is always named first.
D. In an ionic compound, the positive ion is the anion, the negative ion is the cation, and the cation
is always named first.

Answers

Answer:

I think it's c I hope this helps

Under which set of conditions do real gases deviate the most from the ideal gas law?

Answers

Answer:

In summary, a real gas deviates most from an ideal gas at low temperatures and high pressures. Gases are most ideal at high temperature and low pressure. What factors attributes to the deviation of gas law from the ideal gas theory?

Explanation:

Real gases deviate the most from the ideal gas law under low temperature and high pressure.

What is the ideal gas law?

Ideal gas laws say about hypothetical gases, the collision between the molecules of an ideal gas would be perfectly elastic.

There are three variables of an ideal gas, absolute temperature, pressure, and volume.

PV = nRT

Thus, real gases deviate the most from the ideal gas law under low temperature and high pressure.

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What is the second quantum number of a 3p3 electron in phosphorus 1s22s22p63s23p3

Answers

The second quantum number of a 3p₃ electron in phosphorus 1s2, 2s2, 2p6, 3s2, 3p3 is 3.

What are quantum numbers?

Quantum numbers are a set of numbers that describe the position and energy of an electron in an atom.

Principal, azimuthal, magnetic, and spin quantum numbers are the four types of quantum numbers.

Thus, the second quantum number of a 3p₃ electron in phosphorus 1s2, 2s2, 2p6, 3s2, 3p3 is 3.

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