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A. The initial mass of the sample is 6.35

B. The time taken for 0.3 mg of the sample to remain is 66 days

A. Determination of the initial mass of the sample

Half-life (t½) = 15 days

Time (t) = 10 days

n = t / t½

n = 10 / 15

Number of half-lives (n) = ⅔

Amount remaining (N) = 4 mg

[tex]N_0 = N \times {2}^{n} \\ N_0 = 4 \times {2}^{2 \div 3} \\ N_0 = 6.35 \: mg[/tex]

Therefore, the initial mass of the sample is 6.35 mg

B. Determination of the time

Amount remaining (N) = 0.3 mg

Initial amount (N₀) = 6.35 mg

[tex]{2}^{n} = \frac{N_0}{N} \\ \\ {2}^{n} = \frac{6.35}{0.3} \\ \\ {2}^{n} = 21.167 \\ take \: the \: log \: of \: both \: side \\ log \: {2}^{n} = log \: 21.167 \\ nlog2 = log \: 21.167 \\ divide \: both \: side \: by \: log2 \\ \\ n = \frac{log \: 21.167}{log2} \\ \\ n = 4.4[/tex]

Number of half-lives (n) = 4.4

Half-life (t½) = 15 days

t = n × t½

t = 4.4 × 15

Therefore, it will take 66 days for 0.3 mg of the sample to remain.

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MgCl2 product in the reaction forms a precipitate because it is solid an insoluble salt and not dissolve in solution and precipitate on the bottom surface of the solution.

The chemical reaction in which two ionic bond combine to form an insoluble salt in a aqueous solution is called precipitation reaction.

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Answer:

complementary colour

Explanation:

The complementary colors are used for the light that is transmitted when complex ions absorb wavelength of visible light.

Complementary colors are color pairs that cancel each other whenever combined and mixed, resulting in a grayscale color either white or black. They offer the most contrast for the those two hues when put adjacent to each other. Colors that are complementary are sometimes known as "opposite colors."

Light, often known as visible light, is electromagnetic radiation that falls within the region of the electromagnetic spectrum which the human eye can perceive.

Therefore,  the complementary colors are used for the light that is transmitted when complex ions absorb wavelength of visible light.

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Answer:

This is what could happen:

Explanation:

When lava meets ice, the resulting mess can cause flooding, destroy valuable resources and even produce explosions.

Answer:    When lava meets ice, it neither explodes nor tunnels through; rather, it forms strange-looking bubbles.

Explanation:

Answer:

true

Explanation:

hope this helps

Answer:

the anwser is landforms can be created by erosion

Explanation:

The final pressure in the heated can is 2.51 atm

From the question given above, the following data were obtained:

Initial temperature (T₁) = 25 °C = 25 + 273 = 298 K

Initial pressure (P₁) = 1 atm

Final temperature (T₂) = 475 °C = 475 + 273 = 748 K

The final pressure can be obtained as illustrated below:

[tex] \frac{P_1}{T_1} = \frac{P_2}{T_2} \\ \\ \frac{1}{298} = \frac{P_2}{748} \\ \\ cross \: multiply \\ \\ 298 \times P_2 = 1 \times 748 \\ \\ divide \: both \: side \: by \: 298 \\ \\ P_2 = \frac{748}{298} \\ \\ P_2 = 2.51 \: atm[/tex]

Therefore, the final pressure in the heated can is 2.51 atm

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The orientation of the poles of the magnet on the cars and the large

magnet are like poles.

The correct responses are;

First question

Second question:

Third question:

Fourth question:

Reasons:

Potential energy is the energy an object has due to its location.

Energy is a product of force and distance, and therefore, if the force,

experienced by the object increase, the potential energy of the object

increases.

The strength of a magnetic field, B, is given by the formula;

[tex]\displaystyle B = \frac{\mu_0 \cdot I}{2 \cdot \pi \cdot d}[/tex]

Where;

B = The magnetic field strength

I = Current

d = The distance from the source of the magnet

μ₀ = The permeability of free space = 4·π × 10⁻⁷ T m/A

Therefore, the strength of the magnet is higher closer to the source.

First question

In a magnet, like poles push each other back, and given that the poles of the magnet adjacent to each other are like poles, to get the largest increase in she should move the cars towards the large magnet.

Second question:

The reason why the movement will result in the largest increase in potential energy is because like polls repel each other and the strength of a magnetic field increases closer to the magnet

Third question:

The magnetic force that will act on the roller coaster car moved towards the large magnet, pushes the car in the opposite direction.

Fourth question:

The green cart should be moved from point D to point C to get the largest potential energy

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Answer:

The mass of an atom based on the mass of an atom of carbon-12

Explanation:

Answer:

The actinides and the lanthanides

Answer:In a metal, atoms readily lose electrons to form positive ions (cations). These ions are surrounded by delocalized electrons, which are responsible for conductivity.

Explanation:

Due to the structure of ionic compounds, in a crystal of an ionic compound, each cation is surrounded by a number of oppositely-charged anions.

Ionic compounds are compounds that are composed of oppositely charged ions held together by strong electrostatic forces of attraction.

The ions present in an ionic compound are the positively-charged ions known as cations and the negatively-charged ions known as anions.

Each of the oppositely-charged ions are attracted to each other.

Therefore, in a crystal of an ionic compound, each cation is surrounded by a number of oppositely-charged anions.

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Denitrifying Bacteria such as Pseudomonas aeruginosa is the type of bacteria that use enzyme nitrate reductase to metabolise nitrogen oxides to nitrogen gas.

Denitrification is the process whereby nitrites or nitrogen oxides is converted to nitrogen gas by a denitrifying Bacteria such as Pseudomonas.

Pseudomonas aeruginosa uses enzyme nitrate reductase to reduce nitrate to nitrite.

Then nitrite is then converted back to nitrogen gas.

Therefore, Pseudomonas aeruginosa is a type of bacteria that uses enzyme nitrate reductase.

Answer:

see answer

Explanation:

DO the postulates of Daltons atomic theory explain the law of conservation of mass and the law of constant composition.

1. Everything is composed of atoms, which are the indivisible building blocks of matter and cannot be destroyed or divided any further.

2. All atoms of a single pure element are the same in size and mass

3. Atoms of different elements vary from each other in size and mass.

4. Compounds are produced through different simple whole-number combinations of atoms to produce molecules.  

5. Anywhere a compound exists, it will have the same atoms in the same ratio.

6. A chemical reaction between compounds is a re-arrangement of atoms

The law of conservation of mass is shown in 2, 4. and 5.

The law of constant co,position is shown in 2, 4, 5, and 6

Answer: hydrogen chloride.

Explanation:

Answer:

Callable or redeemable bonds

Explanation:

"..are bonds that can be redeemed or paid off by the issuer prior to the bonds' maturity date."

the answer is B. 2

because there is 2 iron on the right side so you need another two on the left side to balance it out

Answer:

No it is not a good conductor

Explanation:

Krypton is classified as a gas and nonmetal. Like many nonmetals and gases, krypton is an insulator, so it is a relatively poor conductor of heat and electricity.

the answer is using rollers in conjunction with inclined plane.

Answer:

(C) Both of these

Explanation:

A beam of electrons has both of these Wave properties and Particle properties.

Can you please add a picture of the case??

Explanation:

According to Charles law : V/T=k (constant).

the volume temperature relationship will be

V/T = 117.5/25 = 4.7

hope this helps you.

Answer:

B- electrons, A- periods, B- groups

Explanation:

Answer:

Sound Travels

Explanation:

Sound waves can travel, and that makes it so that even though Marco is in a different room, he can hear the music. Depending how loud the music is and how thick the walls car, the sound can travel through the walls.

Answer:

Respiratory gas exchange

Explanation:

Answer:

its obviously a chemical change

Explanation: Facts

The addition of the food color in water only causes the change in the cor of water but no new substance is formed. Therefore, the teacher is restarting the physical change.

A physical change can occur when the characteristics of the matter change but the identity does not. Physical changes are classified as: reversible and irreversible. For example, the melting of water is reversible in nature since the melted ice cube will be refrozen.

Physical change can be described as a kind of change where only physical properties of matter such as odor, color, solubility, etc. can change. During physical changes, there is no chemical bonds are broken or formed between atoms of the substance.

The chemical composition as well as the chemical nature of the substance remains unchanged during a physical change.  The molecules of matter can rearrange without changing the internal composition of matter.

Therefore, adding food color to water is a physical change as no new substance formed.

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Answer:

Cl < P < Mg < Na

Explanation:

Cl must have the smallest radius because it is located to the right of the remaining elements on the same row. P  must have the second smallest radius because it is located to the right of the remaining elements on the same  row. Mg must have the Third smallest radius because it is located to the right of Na on the same row.  Therefore, Na has the Largest radius.

I hope it helps.

Despite this problem misses out crucial information for its solution, it turned out possible to come up with the attached absorbance graph, which shows the behavior of the absorbance of the sample with respect to the concentration at 453 nm.

As you can see, there is a red line and circle pointing out the concentration at which the sample has an absorbance of 0.20 (y-axis) which turns out to be 4x10⁻⁵ M (x-axis).

Now, since we require the moles of the iron (III) ions present in 100. mL of the sample, we recall the concept of molarity, which requires moles and volume in liters:

[tex]M=\frac{n}{V}[/tex]

Thus, since all the Fe⁺² in FeSCN⁺² is converted to Fe⁺³ we can find out the moles as shown below:

[tex]n=4x10^{-5}\frac{mol}{L} *0.100L\\\\n=4x10^{-6}mol[/tex]

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