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 describes the equivalence point on a graph of pH versus the amount of titrant added to a solution ​

Answers

Answer:

Titrant and analyte is a pair of acid and base. ... Equivalence point: point in titration at which the amount of titrant added is just enough to completely neutralize the analyte solution. At the equivalence point in an acid-base titration, moles of base = moles of acid and the solution only contains salt and water.

Explanation:

What property did mendeleev use to organize the periodic table.

Answers

Answer:

Atomic weight.

Explanation:

Hope this helps you!

A container with a volume 2. 0 L is filled with a gas at a pressure of 1. 5 atm. By decreasing the volume of the container to 1. 0 L, what is the resulting pressure? Type in your answer using the correct number of significant figures. Remember to use the formula for Boyle's law: P1V1 = P2V2 atm.

Answers

The resulting pressure of the gas after decreasing the initial volume from 2 L to 1 L is 3 atm.

What is Boyle's Law?

According to the Boyle's Law at constant temperature, pressure of the gas is inversely proportional to the volume of that gas.

For the given question we use the below equation is:

P₁V₁ = P₂V₂, where

P₁ = initial pressure of gas = 1.5 atm

V₁ = initial volume of gas = 2 L

P₂ = final pressure of gas = ?

V₂ = final volume of gas = 1 L

On putting all these values on the above equation, we get

P₂ = (1.5atm)(2L) / (1L) = 3 atm

Hence required pressure of the gas is 3 atm.

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Nitrogen (atomic number 7) and phosphorus (atomic number 15) belong to group 15 of the Periodic Table. Write the electronic configuration of these two elements. Which of these will be more electronegative? Why?​

Answers

Answer:

Electronic configuration of nitrogen: K=2 L=5

Electronic configuration of phosphorus : K = 2 L = 8 M = 5

The element nitrogen will be more electronegative because of the smaller size of its atom. nitrogen accepts electrons more easily.

Explanation:

Explanation:

The atomic number of nitrogen is 7 , so its electronic configuration will be 2 , 5The atomic number of phosphorus is 15 , so its electronic configuration is 2 , 8, 5

Nitrogen is more electronegative than phosphorus.

Reason :-

From top to bottom down a group, electronegativity decreases.

Explanation :-

Number of shell increases down a group, so there is an increased distance b/w the valence electrons and nucleus, or a greater atomic radius.‎ ‎

       Since nitrogen has a smaller atomic radius than phosphorus, the attraction of its nucleus towards the incoming electron is more than phosphorus. So , because of smaller atomic size nitrogen accepts electrons more easily.

What is the molarity of 20g of KNO, in 250 mL of water?

Answers

Answer:

should be 2M

Explanation:

:)

A student has a sample of isopropanol (C3H7OH) that has a mass of 78. 6 g. The molar mass of isopropanol is 60. 1 g/mol. How many moles of isopropanol are contained in this sample? 0. 765 moles 1. 31 moles 78. 6 moles 4,720 moles.

Answers

Mole is the ratio of the mass to the molar mass of the substance and its unit is mol. The moles of isopropanol in the sample are 1. 31 moles.

What are moles?

Moles are the unit of measurement of the smallest entity of atoms, molecules, and compounds.

Given,

Mass of isopropanol (m) = 78. 6 g

Molar mass of isopropanol = 60. 1 g/mol

Moles of isopropanol is calculated as:

[tex]\begin{aligned} \rm moles (n) &= \rm \dfrac{mass}{molar \; mass}\\\\&= \dfrac{78.6}{60.1}\\\\&= 1.31\;\rm moles\end{aligned}[/tex]

Therefore, moles of isopropanol are option b. 1.31 moles.

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By titration, 13.5 mL of aqueous H2SO4 neutralized 21.8 mL of 0.0419 M LiOH solution. What was the molarity of the aqueous acid solution?

Answers

13.5 mL of 0.0339 M H₂SO₄ is titrated with 21.8 mL of 0.0419 M LiOH.

What is titration?

Titration is a process of chemical analysis in which the quantity of some constituent of a sample is determined by adding to the measured sample an exactly known quantity of another substance with which the desired constituent reacts in a definite, known proportion.

Step 1: Write the balanced equation.

H₂SO₄ + 2 LiOH ⇒ Li₂SO₄ + 2 H₂O

Step 2: Calculate the reacting moles of LiOH.

0.0218 L × 0.0419 mol/L = 0.000913 mol

Step 3: Calculate the reacting moles of H₂SO₄.

The molar ratio of H₂SO₄ to LiOH is 2:1.

0.000913 mol LiOH × (1 mol H₂SO₄/2 mol LiOH) = 0.000457 mol H₂SO₄

Step 4: Calculate the molarity of H₂SO₄.

[H₂SO₄] = 0.000457 mol/0.0135 L= 0.0339 M

13.5 mL of 0.0339 M H₂SO₄ is titrated with 21.8 mL of 0.0419 M LiOH.

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how many atoms of HCl are needed to produce 0.62 moles of hydrogen gas​

Answers

Answer:

0.2 moles

Explanation:

The equation is given by;

2HCl => H² + Cl²

According to stoichiometry;

[tex] \frac{n \: hcl}{2} = \frac{n \: h {}^{2} }{1} [/tex]

[tex]nhcl = 2 \times nh {}^{2} [/tex]

To produce 0.62 moles of H² gas we need,

nHCL=2×0.62=1.24 moles

Using the relation;

number of moles:Number of atoms/Avogadro's constant

We can then say;

N(numb. of atoms)=n×Na

Number of atoms=1.24×6.02×10²³

Number of atoms=7.5852×10²³ atoms

What is equation for photosynthesis

Answers

Answer: The process of photosynthesis is commonly written as: 6CO2 + 6H2O → C6H12O6 + 6O2. This means that the reactants, six carbon dioxide molecules and six water molecules, are converted by light energy captured by chlorophyll (implied by the arrow) into a sugar molecule and six oxygen molecules, the products.

hope this helps!

Answer:

6CO2 + 6H2O → C6H12O6 + 6O2

Explanation:

The specific heat capacity of iron 0. 45 j/gk. Find the molar heat capacity for iron

Answers

Answer:

The final temperature of the sample is 21.004 °C

Explanation:

The molar heat capacity for iron is 25.130 J/g.c joules per gram per Kelvin.

What is molar heat capacity?

The amount of heat needed to increase one temperature of one mole of a substance is called molar heat capacity.

By the formula [tex]\rm \Delta T^\circ c = \Delta Tk[/tex]

Given that c = 0.45 J/g.C

Molar mass of iron is 55.845

Then putting the values in the equation

[tex]c= 0.45 \times 55.845 \\\\c= 25.130 \;J/g.^\circ c[/tex]

Thus, the molar heat capacity for iron is 25.130 J/g.c

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Carbon is the main constituent of hydrocarbons. Why some are called unsaturated hydrocarbon? Briefly describe.

Answers

Some hydrocarbons are regarded as unsaturated because they contain double or triple bonds between adjacent carbon atoms.

What are hydrocarbons?

Hydrocarbons are any organic compounds that contain hydrogen and carbon in its structure.

Hydrocarbons can be grouped into the following based on whether they contain single or double bonds:

Saturated hydrocarbons - contain only single bonds e.g. alkanesUnsaturated hydrocarbons - contain double and triple bonds e.g. alkenes

Therefore, it can be said that some hydrocarbons are regarded as unsaturated because they contain double or triple bonds between adjacent carbon atoms.

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Explain how sulfur forms its ion.

Answers

Explanation:

the sulfur ato is in group 6 of the periodic table. In order to become an ion the ato needs to gain 2 electrons so it has a full outer shell of electron and is stable. so the atom S goes to S2+ + 2e

476 nm = [? ]10
cm
give your answer in scientific notation.

Answers

1nm=10^-6 cm.

476 nm = 4.76E-5 cm

Marble(calcium carbonate) reacts with hydrochloric acid(hcl) to form calcium chloride solution, water, and carbon dioxide. Find the percent yield of carbon dioxide if 3. 65 grams

Answers

Answer:

When calcium carbonate reacts with hydrogen chloride, it reacts to form calcium chloride, carbon dioxide, and water. If this reaction occurs with 51.6% yield, what mass of carbon dioxide will be collected if 16.93 g of CaCO3 is added to sufficient hydrogen chloride

chinua reacts 37g of magnesium with 150g of sulfuric acid. what will be the total mass of the products of this reaction

Answers

the total mass is 187g. The total mass of the reactant is always equal to total mass of the products.

explanation:

as per the given details, the reactant involved in the reaction are 37g of magnesium and 150g of sulfuric acid . the total of the reactant is 187g.

Would the ph at the equivalence point be acidic, basic, or neutral for each given titration?.

Answers

The pH at equivalence point depends on the nature of the acid-base titration, and can either be acidic, basic, or neutral.

What is equivalence point?

The equivalence point in a titration is the point at which equal amount of acid and base have reacted with each other.

The pH at equivalence point depends on the nature of the acids and bases being titrated.

pH at equivalence point will be:

neutral in a strong acid and strong base titrationacidic in a strong acid and weak base titration basic in a weak acid and strong base titration

Therefore, the pH at equivalence point depends on the nature of the acid-base titration.

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How are Dams good and Bad for the environment?

Help!!

Answers

Answer:

Dams can stop a place from flooding and give us electricity without creating pollution. It can also make a place dry and finish water for animals

Explanation:

are frosted flakes healthier than fruit loops?

Answers

No

Frosted flakes are rich in carbohydratesCarbohydrates are good for energy but they are life risky and can cause diabetes.Where as fruit loops are rich in several minerals and vitamins So fruit loops are healthier

Write balanced equations and expressions for ksp for the dissolution of each of the following ionic compounds. Write a balanced equation for the dissolution of baso4

Answers

Based on the dissolution equation of BaSO4, the solubility product, Ksp, expression of BaSO4 is: [Ba^{2+}] × [SO4^{2-}]

What is solubility product Ksp of a solute?

The solubility product, Ksp, of a substance is an equilibrium constant which expresses the product of the concentration of ions produced by a solute.

The solubility of a solute depends on temperature, thus solubility product also depends on temperature.

The balanced equation for the dissolution of barium sulfate is given below:

BaSO4 ⇌ Ba^{2+} + SO4^{2-}

The solubility product for barium sulfate is given as;

Ksp = [Ba^{2+}] × [SO4^{2-}]

Therefore, the solubility product, Ksp, expression of BaSO4 is: [Ba^{2+}] × [SO4^{2-}]

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If 550 mL of a 3.50 M KCl solution are set aside and allowed to evaporate until the volume of the solution is 275 mL, what will the molarity of the solution be?

Answers

Answer:

Explanation:

Molarity = number of moles / volume

If 550 mL of a 3.50 M KCl solution are set aside and allowed to evaporate until the volume of the solution is 275 mL, which is half of 550 mL, the molarity of the solution with the same number of moles of KCl is 3.5 * 2 = 7.00 M

The molarity of the solution will be 7 M.

What is  molarity ?

The total count of moles of solute per liter of a particular solution is known as a solution's molarity.

What is solution?

The volume of just an object is a measurement of how much space it takes up.

Molarity of the solution can be determined by the formula:

[tex]M_{1} V_{1} = M_{2} V_{2}[/tex]

where, M = molarity of solution. V = volume.

Given data:

[tex]M_{1}[/tex] = 3.50 M

[tex]M_{2}[/tex] = ?

[tex]V_{1}[/tex] = 550 mL

[tex]V_{2}[/tex] = 275 mL

Now, put the value of given data in molarity equation.

[tex]V_{2} = M_{1} V_{1} /M_{2}\\V_{2} = (3.50 M) (550 mL) / (275 mL)\\V_{2} = 7 M[/tex]

Therefore, the molarity of the solution will be 7 M.

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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

Convert 18◦C to Kelvin.

Answers

291.15 Kelvin

I hope this helps

Answer:

18 degrees Celsius = 291.15 Kelvin

Explanation:

The formula for finding Kelvin through Celsius is by adding 273.15 to the Celsius. In this case, it is 18 + 273.15 = 291.15

:)

Which is a disadvantage of using chemical indicators? they are expensive to use. they measure ph directly. they must be selected for a narrow ph range. they do not use electricity to operate.

Answers

Chemical indicators are the chemical reagents that show the change in reaction by changing color. Chemical indicators must be chosen with a narrow pH range.

What are indicators?

Indicators are the solutions or the substances used for the qualitative and the quantitative measurement by a change in color because of the absence or the presence of the sample concentration.

The chemical indicators cannot detect the exact pH and should be used with a narrow range of pH.

Therefore, option C. the narrow range of pH is the disadvantage of chemical indicators.

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Answer:

C (They must be selected for a narrow ph range.

Explanation:

Edg 2022

Do the halogens tend to gain or lose electrons in chemical reactions? how many?

Answers

Explanation:

Halogens tend to gain one electron so that they can get a full outer level and be stable.

A quantity of helium gas occupies 5 liters at room temperature and standard atmospheric
pressure (760 mm Hg). If the temperature stays the same, what will be the volume o
the helium if the pressure is increased to 950 mm of mercury?

Answers

The new volume of occupied by helium gas when its pressure is increased from 760 mm Hg to 950 mm Hg at an initial volume of 5 L is equal to 4 L.

Boyle's Law

Boyle's law state that at constant temperature, the volume of a fixed mass of gas is directly proportional to its pressure.

To calculate the volume of the helium gas, we use the formula below.

Formula:

P₁V₁ = P₂V₂............. Equation 1

Where:

P₁ = Initial pressureV₁ = Initial volumeP₂ = Final pressureV₂ = Final volume.

Make V₂ The subject of the equation

V₂ = P₁V₁/P₂............... Equation 2

From the question,

Given:

P₁ = 760 mm HgV₁ = 5 LP₂ = 950 mm Hg

Substitute these values into equation 2

V₂ = (760×5)/950V₂ = 4 L.

Hence, The new volume of occupied by helium gas when its pressure is increased from 760 mm Hg to 950 mm Hg at an initial volume of 5 L is equal to 4 L.

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1. Describe the liquid state according to the
kinetic-molecular theory.

Answers

Answer:

Liquids have more kinetic energy than solids. When a substance increases in temperature, heat is being added, and its particles are gaining kinetic energy. Because of their close proximity to one another, liquid and solid particles experience intermolecular forces. These forces keep particles close together.

Explanation:

hope it helps U

Calculate the Gibbs energy, entropy, and enthalpy of mixing when 1.00mol C6H14 (hexane) is mixed with 1.00mol C7H16 (heptane) at 298K. Treat the solution as ideal.

Answers

With Hexane of 1.00 ml and 1.00 ml of hectane at 298, the calculated

Gibbs energy = 3.43Entropy = -3.43Enthalpy = 0

How to solve for the Gibbs energy

C6H14 = C6H14/C6H14+C7H16

1mol/1mol+1mol = 1/2 = 0.5 mol

1+1 x 8.3145J x 298 x 0.5ln0.5 + 0.5ln0.5

= 4955.442 0.6932

= 3435J

convert to KJ

G mix = 3.43

The Gibbs energy is therefore  3.43KJ/mol

The entropy of the solution

-(1+1 x 8.3145J x 298 x 0.5ln0.5 + 0.5ln0.5)

S mix = -3.43 KJ/mol

3.43/298 = 11.5

The enthalpy of the solution

3.43-3.43 KJ/mol

H mix = 0

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Do you think that parents should be able to design their babies using gene technology such as CRISPR?

Make sure you have 4 or 5 sentences for your answer.

Answers

Answer:

When Chinese researchers first edited the genes of a human embryo in a lab dish in 2015, it sparked global outcry and pleas from scientists not to make a baby using the technology, at least for the present.

When Chinese researchers first edited the genes of a human embryo in a lab dish in 2015, it sparked global outcry and pleas from scientists not to make a baby using the technology, at least for the present.It was the invention of a powerful gene-editing tool, CRISPR, which is cheap and easy to deploy, that made the birth of humans genetically modified in an in vitro fertilization (IVF) center a theoretical possibility

Explanation:

Now, it appears it may already be happening.

According to Chinese medical documents posted online this month (here and here), a team at the Southern University of Science and Technology, in Shenzhen, has been recruiting couples in an effort to create the first gene-edited babies. They planned to eliminate a gene called CCR5 in hopes of rendering the offspring resistant to HIV, smallpox, and cholera.

Some bacteria live in the roots of plants like soybeans and peas.

Bacteria growing on plant roots.
What is the role of these bacteria in the nitrogen cycle?

to absorb nitrogen-containing compounds from the soil
to release free nitrogen into the atmosphere
to break down nitrogen-containing compounds in dead organisms
to convert free nitrogen into usable nitrogen

70 points!

Answers

Answer:

to release free nitrogen into the atmosphere. This is the answer.

Answer:

to convert free nitrogen into usable nitrogen

Explanation:

got it right on the test boi

Given what you observe at the molecular/atomic level, why would surface area have this effect?

Answers

Answer:

Increasing the surface area of a reactant increases the frequency of collisions and increases the reaction rate. Several smaller particles have more surface area than one large particle. The more surface area that is available for particles to collide, the faster the reaction will occur.

Explanation:

:)

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