why does it take much longer for a car to stop when applying the brakes at a speed of 60 miles per hour then it 50 miles per hour

After three half-lives, 12.5% of the original radioactive parent isotope will remain.

To determine the remaining amount of a radioactive parent isotope after a given number of half-lives, you need to understand the concept of radioactive decay.

A radioactive isotope undergoes decay, reducing its quantity over a set period known as a half-life.

Each half-life represents the time it takes for half of the parent isotope to decay into a daughter isotope.

Explanation and Calculation:

1. Concept of Half-Life:

- A half-life is the time required for half of the radioactive parent isotope to decay.

2. Formula for Remaining Fraction:

- The fraction of the parent isotope remaining after n half-lives can be calculated using the formula:

[tex]\[ \left(\frac{1}{2}\right)^n \][/tex]

- Here, n is the number of half-lives.

3. Calculation for Three Half-Lives:

[tex]\text{After 1 half-life:} \\\\\left(\frac{1}{2}\right)^1 = \frac{1}{2} = 0.5 \text{ (50\% remains)}\\\text{After 2 half-lives:} \\\\\left(\frac{1}{2}\right)^2 = \frac{1}{4} = 0.25 \text{ (25\% remains)}\\\text{After 3 half-lives:} \\\\\left(\frac{1}{2}\right)^3 = \frac{1}{8} = 0.125 \text{ (12.5\% remains)}[/tex]

Conclusion:

Thus, after three half-lives, only 12.5% of the original parent isotope remains. This is calculated using the formula [tex]\(\left(\frac{1}{2}\right)^n\)[/tex], where n is the number of half-lives.

2.72 moles of HF are needed to react with 0.340 mol of Na₂SiO₃ based on the balanced chemical equation.

To determine how many moles of HF are needed to react with 0.340 mol of Na₂SiO₃, we need to look at the balanced chemical equation:

Na₂SiO₃(s) + 8 HF(aq) -> H₂SiF₆(aq) + 2 NaF(aq) + 3 H₂O(l)

The balanced equation shows that 1 mole of Na₂SiO₃ reacts with 8 moles of HF. Therefore, to find the moles of HF needed for 0.340 mol of Na₂SiO₃, we use the ratio:

(0.340 mol Na₂SiO₃) * (8 mol HF / 1 mol Na₂SiO₃) = 2.72 mol HF

Therefore, 2.72 moles of HF are needed to react with 0.340 mol of Na₂SiO₃.

higher gas pressure

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Final answer:

A polar covalent bond is a type of covalent bond with unequal sharing of electrons due to a difference in electronegativity between the bonded atoms, leading to a partial negative and positive charge on the atoms.

Explanation:

The best definition of a polar covalent bond is a type of covalent bond in which the electrons are shared unequally between the bonded atoms. This disparity in sharing occurs because the atoms involved have different electronegativities - a measure of how strongly an atom attracts electrons in a bond.

When the difference in electronegativities between the two atoms falls between 0.4 and 1.7, the electrons are not shared equally, leading to a polar bond. One atom attracts the shared electrons more strongly, giving it a partial negative charge, while the other atom acquires a partial positive charge, creating a dipole.

In contrast, a nonpolar covalent bond occurs when the electronegativity difference is less than 0.4, resulting in equal sharing of electrons and no dipole. On the opposite end of the spectrum, if the difference in electronegativity is greater than 1.7, it may lead to an ionic bond, where electrons are transferred rather than shared.

A polar covalent bond is a type of covalent bond where the electrons are shared unequally between the bonded atoms.

This happens because the atoms involved have different electronegativities, meaning one atom attracts the shared electrons more strongly than the other. Typically, if the difference in electronegativity between the atoms is between 0.4 and 1.7, the bond is considered polar covalent.

Due to this unequal sharing, the molecule has regions with partial positive and partial negative charges, leading to an imbalance in electron distribution. These partial charges create a dipole moment within the molecule, making it polar.

Answer:

protons in the atom

Explanation:

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Atoms Quiz- Grade 8 Unit 2 Lesson 2

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We balance the given redox reaction using the half-reaction method. First, we write the half-reactions, balance atoms other than H and O, balance O by adding H2O, balance H by adding H+ ions, and ensure electrical neutrality by adding electrons. The result is the balanced reaction: 2Ag + clo2- + 2H2O → 2Ag + clo4- + 4H+.

The task is to balance a redox reaction wherein clo2– is oxidized to clo4– and Ag is reduced to Ag in an acidic solution. We do this by employing a method known as the half-reaction method which involves the following steps:

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Answer : The correct option is, [tex]6.0\times 10^{-5}M[/tex]

Explanation :  Given,

pOH = 4.22

pOH : It is defined as the negative logarithm of hydroxide ion concentration.

Now we have to calculate the [tex]OH^-[/tex] concentration.

Formula used :

[tex]pOH=-\log [OH^-][/tex]

Now put all the given values in this formula, we get the concentration of hydroxide ion.

[tex]4.22=-\log [OH^-][/tex]

[tex][OH^-]=6.0\times 10^{-5}M[/tex]

Therefore, the [tex]OH^-[/tex] concentration is, [tex]6.0\times 10^{-5}M[/tex]

Answer: Option (c) is the correct answer.

Explanation:

It is necessary to take precautions while performing an experiment in a laboratory. This is because safety measures in the laboratory can prevent any serious injury.

For example, when accidentally an acid spills on Celia's hand then it is important to inform the teacher about it while Celia washes her arm with soap and water.

Also, when doing an experiment or dealing with acids the we should be wearing lab coat, safety goggles, closed shoes and safety gloves.

Thus, we can conclude that out of the given options, Lee should tell the teacher while Celia washes her arm with soap and water, this should be done next.

Answer:508

Explanation:

I saw from another post or actually 507.8

When reporting the mass of the NaCl sample, consider the number of significant figures. The precision of the measurement equipment determines the appropriate number of significant figures to report.

When reporting the measurement of the mass of the NaCl sample, you should consider the significant figures. Significant figures are the digits in a number that carry meaning and contribute to its precision. In general, you should report your measurement to the same number of significant figures as the least precise measurement involved in the calculation.

In the given question, there is no specific information provided about the NaCl sample and the precision of the measurement. Therefore, it is not possible to determine the accurate number of significant figures to report. However, it is important to determine the precision of the equipment used to measure the mass and report the measurement accordingly.

Answer:

522.2kJ

Explanation:

Hello,

In this case, based on the given conversion data, we apply the following proportional factor to obtain the corresponding energy in kJ:

[tex]125cal*\frac{4.18kJ}{1cal}=522.2kJ[/tex]

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Answer:

B) Nitrogen monoxide gas plus hydrogen gas yields ammonia gas plus water vapor

Explanation:

The given reaction is:

[tex]2NO(g) + 5H_{2}(g)\rightarrow 2NH_{3}(g)+ 2H_{2}O(g)[/tex]

Here the chemical names of the reactants are:

NO = nitric oxide or nitrogen monoxide in gas phase

H2 = hydrogen gas

NH3 = ammonia in gas phase

H2O = water in gas phase i.e. vapor

Therefore the reaction can be expressed in words as:

Nitrogen monoxide gas plus hydrogen gas yields ammonia gas plus water vapor

Answer:

The diagonal rule states that electrons fill orbitals in order of increasing "quantum number sum" (n + ℓ). When two orbitals share the same "quantum number sum", they will be filled in order of increasing n.

Explanation:The electrons in an atom fill up its atomic orbitals according to the Aufbau Principle; "Aufbau," in German, means "building up." The Aufbau Principle, which incorporates the Pauli Exclusion Principle and Hund's Rule prescribes a few simple rules to determine the order in which electrons fill atomic orbitals:

Electrons always fill orbitals of lower energy first. 1s is filled before 2s, and 2s before 2p.

The Pauli Exclusion Principle states no two electrons within a particular atom can have identical quantum numbers. In function, this principle means that if two electrons occupy the same orbital, they must have opposite spin.

Hund's Rule states that when an electron joins an atom and has to choose between two or more orbitals of the same energy, the electron will prefer to enter an empty orbital rather than one already occupied. As more electrons are added to the atom, these electrons tend to half-fill orbitals of the same energy before pairing with existing electrons to fill orbitals.

Valence Electrons:

The outermost orbital shell of an atom is called its valence shell, and the electrons in the valence shell are valence electrons. Valence electrons are the highest energy electrons in an atom and are therefore the most reactive. While inner electrons (those not in the valence shell) typically don't participate in chemical bonding and reactions, valence electrons can be gained, lost, or shared to form chemical bonds. For this reason, elements with the same number of valence electrons tend to have similar chemical properties, since they tend to gain, lose, or share valence electrons in the same way. The Periodic Table was designed with this feature in mind. Each element has a number of valence electrons equal to its group number on the Periodic Table.

The solution with a higher concentration of hydroxide ions (oh-) than hydrogen ions (h+) are base solutions or solutions which are the basic  option B is correct.

A solution which is basic in nature in  aqueous solution  they contain   more OH - ions concentration than that of H + ions concentration. that is they are, in  aqueous solution with a pH greater than 7.

Basic solutions contain ions, with some  conducted  electricity, and it turn red litmus paper blue, and slippery while touching.

They are mostly used in the manufacturing of soaps, toothpaste, paper and rayon as they do not react with skin due to basic in nature.

Basic substances react to aqueous solutions by accepting or gaining of  protons, giving away or releasing the  electrons, or releasing and make free hydroxide ions.

Therefore, they are basic solutions. option B is correct

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The given question is incomplete therefore, the complete question is

a solution with a higher concentration of hydroxide ions (oh-) than hydrogen ions (h+)

A.acid

B. base

C.neutral

The true statement about color in a fiber is that the color depends upon the lighting source, because fibers absorb some wavelengths of light and reflect others. Different illumination can change the perceived color of the fiber.

The statement 'the color depends upon the lighting source' is true when considering color in a fiber. The true color of an object, including fibers, is defined by its absorptive or reflective characteristics, which is how the object interacts with various wavelengths of light. When an object is illuminated by white light (a mixture of all visible wavelengths), it reflects some wavelengths while absorbing others; the reflected wavelengths determine the color we perceive. If illuminated by colored light, the object can appear a different color. For example, under pure red light, a blue object will appear black because it absorbs the red light. Furthermore, the color of fibers is not always a result of pigments as structural coloration also exists, and there is a wide variety of dyes that can be used for fibers, not just a few.

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The volume of solid ice is greater than the volume of water. In winter in the absence of heat water in the pipe freezes, as ice takes greater space to fit in than water, the pipe burst in winter in the absence of heating.

Freezing of water is an exothermic process (heat is released by the system into the surrounding) where as melting of ice is an endothermic process (heat is absorbed by the system from the surrounding). If the heat was on it would prevent ice formation in the pipes.

The water pipes burst due to the expansion of water in them.

Water behaves in an anomalous manner. While most substances expand when heated and contract when cooled, water begins to expand at 4°C.

As a result of this, solid water is less dense than liquid water because it has more volume than liquid water.

Since solid water has more volume compared to liquid water, the pipes may no longer be able to contain the expanding water which has turned to ice leading to the bursting of the water pipes.

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The number of molecules resulting from a chemical reaction depends on the balanced chemical equation, which is not provided for the ethanol combustion. We would need this to determine the exact quantities of CO2, H2O, and O2 produced from the reaction involving ethanol.

To determine the number of molecules present after a chemical reaction has gone to completion, we use the balanced chemical equations. However, the initial question does not provide a complete balanced equation for the reactions involving CO2, H2O, C2H5OH (ethanol), and O2 (oxygen). We are provided information about the combustion of methane and the reaction of propane but not the specific reaction for ethanol, which is necessary to determine the exact number of molecules produced in its combustion.

Given the example of the propane combustion, which yields 3 moles of CO2 and 4 moles of H2O from 0.75 mol of propane, we can extend this stoichiometric ratio to determine the number of molecules. The number of molecules produced from the combustion of a known quantity of another substance, like ethanol, would depend on its stoichiometry. Without the balanced equation for ethanol combustion, we cannot calculate the exact quantities of CO2, H2O, and O2 produced. Therefore, the student should provide the complete balanced chemical equation or clarify if the question is about a different reaction than the ones provided.

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Jon and Katarina use the same method for completing a lab report because they are both using scientific inquiry to conduct their experiments.

Jon and Katarina use the same method for completing a lab report because they are both using scientific inquiry to conduct their experiments. The scientific method is a process that scientists follow to gather information, form hypotheses, test their hypotheses through experiments, and draw conclusions based on their results. It is a systematic and organized approach that can be applied to various scientific disciplines, including chemistry and geology.

Answer:

The emission of free carriers or electrons taking place when light falls into a substance is termed as the photoelectric effect. On the basis of the Rutherford model, the light of any energy should possess the tendency to cause the electrons to leave the atom and get emitted.  

The energy obtained from the emitted electrons should be associated with the intensity of the light. However, the energy of the electron is in the real sense only associated with the energy of the light.  

To solve this problem, first we assume the volume is purely additive. The density of the mixture can then be calculated by the summation of mass fraction of each component divided by its individual density:

1 / ρ mixture = (x NH3 / ρ NH3) + (x H2O / ρ H2O)                        ---> 1

Calculating for mass fraction of NH3:

x NH3 = 15 g / (15 g + 250 g)

x NH3 = 0.0566

Therefore the mass fraction of water is:

x H2O = 1 – x NH3 = 1 – 0.0566

x H2O = 0.9434

Assuming that the density of water is 1 g / mL and substituting the known values back to equation 1:

1 / 0.974 g / mL = [0.0566 / (ρ NH3)] + [0.9434 / (1 g / mL)]

ρ NH3 = 0.680 g / mL

Given the density of NH3, now we can calculate for the volume of NH3:

V NH3 = 15 g / 0.680 g / mL

V NH3 = 22.07 mL

The number of moles NH3 is: (molar mass NH3 is 17.03 g / mol)

n NH3 = 15 g / 17.03 g / mol

n NH3 = 0.881 mol

Therefore the molarity of NH3 in the solution is:

Molarity = 0.881 mol / [(22.07 mL  + 250 mL) * (1L / 1000 mL)

M = 3.238 mol/L = 3.24 M

To find the molarity of the NH3 solution, divide the moles of NH3 by the volume of the solution in liters.

To find the molarity of the NH3 solution, we need to first calculate the moles of NH3. We can do this by dividing the mass of NH3 (15.0 g) by its molar mass (17.03 g/mol) to get 0.881 mol. Next, we need to calculate the volume of the solution. Because density is mass divided by volume, we can rearrange the equation to solve for volume, which is mass divided by density. Substituting in the given values, we get 250.0 g / 0.974 g/ml = 256.62 ml. Since 1 ml is equal to 0.001 L, the volume of the solution is 0.25662 L. Finally, we can calculate the molarity by dividing the number of moles of solute (NH3) by the volume of the solution in liters. Substituting the values, we get 0.881 mol / 0.25662 L = 3.43 M.

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