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3 years ago

The half life of Radon-222 is 3.8 days. If you have a 90.0g sample of Radon-222 in the lab, how much will be left after 19 days?

Chemistry

1 answer:

statuscvo [17]3 years ago

5 0

Answer:

half lives passed=5

given sample=90g

sample left=2.8125g

Explanation:

no. of half lives=total time/half life

no.=19days/3.8days

no.=5 days

after 5 half lives sample left=2.8125g

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Which of the following statements is not correct?

Pavlova-9 [17]

Answer: This option is incorrect: <span>B. Covalent compounds are held together by much stronger interparticle forces than are ionic compounds.

Justification:

Ionic bonds, held by ionic compounds, are much stronger than covalent bonds, held by covalent compounds.

In ionic bonds one element yields one or more electrons forming a cation (a positively charged ion) and the other element accepts the electrons forming an anion (a negatively charged ion).

The anion and the cation are electrostatically atracted by each other. This electrostatic atraction force, named ionic bond, is very strong.

As result of this, the ionic compounds form strong crystals with high boiling and fusion points. A good example of this the sodium chloride, formed by the union of cation Na(+) and anion Cl(-).

The covalent bonds are result of sharing electrons and do not form ions. This bond is weaker than the ionic bond.
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3 years ago

Consider a transition of the electron in the hydrogen atom from n=3 to n=7.

kow [346]

<u>Answer:</u>

<u>For a:</u> The wavelength of light is $1.005\times 10^{-6}m$

<u>For b:</u> The light is getting absorbed

<u>Explanation:</u>

<u>For a:</u>

To calculate the wavelength of light, we use Rydberg's Equation:

$\frac{1}{\lambda}=R_H\left(\frac{1}{n_i^2}-\frac{1}{n_f^2} \right )$

Where,

$\lambda$ = Wavelength of radiation

$R_H$ = Rydberg's Constant = $1.097\times 10^7m^{-1}$

$n_f$ = Higher energy level = 7

$n_i$ = Lower energy level = 3

Putting the values in above equation, we get:

$\frac{1}{\lambda }=1.097\times 10^7m^{-1}\left(\frac{1}{3^2}-\frac{1}{7^2} \right )\\\\\lambda =1.005\times 10^{-6}m$

Hence, the wavelength of light is $1.005\times 10^{-6}m$

<u>For b:</u>

There are two ways in which electrons can transition between energy levels:

<u>Absorption spectra:</u> This type of spectra is seen when an electron jumps from lower energy level to higher energy level. In this process, energy is absorbed.
<u>Emission spectra:</u> This type of spectra is seen when an electron jumps from higher energy level to lower energy level. In this process, energy is released in the form of photons.

As, the electron jumps from lower energy level to higher energy level. The wavelength is getting absorbed.

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3 years ago

How does density differ from concentration?

Aliun [14]

The main difference between concentration and density is that concentration refers to how much of a substance is present in a mixture, whereas density refers to the mass of a substance per unit volume.

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3 years ago

A weather balloon is filled with helium that occupies a volume of 5.00 × 10^4 L at 0.995 atm and 32.0°C. After it is released, i

DaniilM [7]

Answer:

The new volume is 5.913*10^4 L

Explanation:

Step 1: Write out the formula to be used:

Using general gas equation;

P1V1 / T1 =P2V2 /T2

V2 = P1V1T2 / P2T1

Step 2: write out the values given and convert to standard unit's where necessary

P1 = 0.995atm

P2 0.720atm

V1 = 5*10^4 L

T1 = 32°C = 32+ 273 = 305K

T2 = -12°C = -12 + 273 = 261K

Step 3: Equate your values and do the calculation:

V2 = 0.995 * 5*10^4 * 261 / 0.720 * 305

V2 = 1298.475 * 10^4 / 219.6

V2 = 5.913 * 10^4 L

So the new volume of the balloon is 5.913*10^4 L

3 0

3 years ago

Which of the following most accurately represents John Dalton’s model of the atom? A. a tiny, solid sphere with an unpredictable

valkas [14]

The most accurately represented John Dalton's model of the atom is: C. a tiny, solid sphere with a predictable mass for a given element

<h3>Further explanation</h3>

The development of atomic theory starts from the first term conveyed by Greek scientists who suggested that every substance has the smallest particles so that the word atomos appears, which means it cannot be divided. So, John Dalton, a British scientist put forward the hypothesis about atoms, among others:

1. The elements are composed of atoms which are small particles which cannot be subdivided

2. Atoms that make up the same element have the same properties, mass, and size, while for different elements, the properties are also different

3. Compounds are composed of two or more atoms in a fixed ratio

4. In chemical reactions, atoms after and before a reaction cannot be destroyed, only separation and reassembly occur

Point 3 shows the relationship with The Law of Constant Composition of Proust so that further research on atoms is more developed

Dalton's hypothesis is described as a solid sphere like a very small shot put ball or a bowling ball based on Dalton's hobby in bowling

<h3>Learn more</h3>

Bohr's model of the atom

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Rutherford performed the gold foil experiment

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The part of an atom that is mostly empty space

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Keywords: atom, Dalton, a solid sphere, The Law of Constant Composition

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3 years ago

Read 2 more answers