what the movement of the earth around the sun​

The half life of a radioactive isotope refers to the time taken for half of the number of original number of atoms present in the sample to decay.

The equation below gives the number of atoms present at time t

[tex]N=Noe^-kt[/tex]

N = Number of atoms present at time t

No = Number of atoms initially present

k = decay constant

t = time taken

Given that;

t1/2 = 0.693/k

where t1/2 = half life

k = 0.693/t1/2

k = 0.693/ 55.6 s

k = 0.0125 s-1

Substituting values;

N = 16,000 e^-0.0125(0)

N = 16,000 atoms

At 50 s

N = 16,000 e^-0.0125(50)

= 8564 atoms

At 100 s

N = 16,000 e^-0.0125(100)

= 4584 atoms

At 200 s

N = 16,000 e^-0.0125(200)

= 1313 atoms

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Answer: Promotion of electrons is accompanied by a release of energy because of absorption of photon.

Explanation:

Promotion of electrons occurs when an electron accepts or absorbs a photon which leads to it's movement from a lower energy level orbital to a higher energy orbital.

According to Bohr, the electrons was restricted to certain energy levels and was thought to move along certain circular orbits around the nucleus. These energy levels were identified by means of principal quantum number, n. The wave mechanics model of atom does not restrict the electrons to a certain energy levels only. Instead it describes a region around the Nucleus called orbitals where there is a possibility of finding an electron with a certain amount of ENERGY.

The energy levels are composed of one or more orbitals and the distribution of electrons around the nucleus is determined by the number and kind of energy levels that are occupied.

Bohr made an assumption that an electron emits energy in the form of radiation when it moves from a higher to a lower permitted orbit, this produces a line in the atomic emission spectrum. Since the energies of the higher and lower orbits are fixed, the line will be of a particular energy and frequency.

Answer:

2.076

Explanation:

1 mole is 6.02 * 10^23

To convert from atoms (or molecules or compounds or ions etc.) to mols, you divide the number of atoms (or molecules or etc.) by 6.02 * 10^23

So it is (1.25 * 10^24)/(6.02 * 10^23)

=2.076

Answer:

[tex]\boxed {\boxed {\sf 2.08 \ mol \ C}}[/tex]

Explanation:

We are asked to convert a number of carbon atoms to moles.

We will use Avogadro's Number for this, which is 6.022 × 10²³. This is the number of particles (atoms, molecules, formula units, etc.) in 1 mole of a substance. For this problem, the particles are atoms of carbon. There are 6.022 ×10²³ atoms of carbon in 1 mole of carbon.

We will also use dimensional analysis to solve this problem. To do this, we use ratios. Set up a ratio using the underlined information.

[tex]\frac {6.022 \times 10^{23} \ atoms \ C}{1 \ mol \ C}[/tex]

We are converting 1.25 ×10²⁴ atoms of carbon to moles, so we multiply the ratio by that value.

[tex]1.25 \times 10^{24} \ atoms \ C* \frac {6.022 \times 10^{23} \ atoms \ C}{1 \ mol \ C}[/tex]

Flip the ratio. It remains equivalent, but it allows us to cancel the units atoms of carbon.

[tex]1.25 \times 10^{24} \ atoms \ C* \frac{1 \ mol \ C} {6.022 \times 10^{23} \ atoms \ C}[/tex]

[tex]1.25 \times 10^{24} * \frac{1 \ mol \ C} {6.022 \times 10^{23} }[/tex]

[tex]\frac{1.25 \times 10^{24} } {6.022 \times 10^{23} } \ mol \ C[/tex]

[tex]2.075722351 \ mol \ C[/tex]

The original measurement of atoms has three significant figures, so our answer must have the same. For the number we calculated, that is the hundredths place. The 5 in the thousandths place tells us to round the 7 up to an 8.

[tex]2.08 \ mol \ C[/tex]

1.25 ×10²⁴ atoms of carbon is equal to approximately 2.08 moles of carbon.

Answer:

1. more

2. less

3. more

4. less

Explanation:

Answer:

It is a combustion reaction.

Answer:

See explanation

Explanation:

The particular reactants in the Fischer esterification reaction were not stated.

Generally, a Fischer esterification is a reaction that proceeds as follows;

RCOOH + R'OH ⇄RCOOR' + H2O

This reaction occurs in the presence of an acid catalyst.

We can shift the equilibrium of this reaction towards the products side in two ways;

I) use of a large excess of either of the reactants

ii) removal of one of the products as it is formed.

Any of these methods shifts the equilibrium of the Fischer esterification reaction towards the products side.

Answer:

an if/then statement

Explanation:

Answer:

can only be determined experimentally.

Explanation:

In the early days of inorganic chemistry, the structure of complex ions remained a mystery hence the name ''complex''.

These ions appear to have structures that defied accurate elucidation. However, by diligent laboratory investigation, Alfred Werner was able to accurately determine the structure of cobalt complexes. As a result of this, he is regarded as a pathfinder in coordination chemistry.

Hence, the structure of complex ions can only be determined experimentally.

Answer:

c. can only be determined experimentally

Explanation:

It is not possible to know for certain the structure of a complex ion on the basis of stoichiometry or by the electrical charges on the components. The structure of the resulting complex ion can only be known by experiment.

Answer:

-31.72°F

Explanation:

(-35.4°C × 9/5) + 32 = -31.72°F

The average temperature at the South Pole In January is - 35.4 °C. This temperature in Fahrenheit is -31.72 °F

To convert Celsius to Fahrenheit, you can use the formula:

°F = (°C × 9/5) + 32

Let's calculate the temperature at the South Pole in degrees Fahrenheit:

°F = (-35.4 × 9/5) + 32

°F = (-63.72) + 32

°F = -31.72

Rounding to three significant digits, the temperature at the South Pole in degrees Fahrenheit is approximately -31.7 °F. The negative sign indicates that the temperature is below the freezing point in both Celsius and Fahrenheit scales. The South Pole experiences freezing temperatures, as it is located near the Earth's southernmost point and experiences long periods of darkness during January.

Hence, the temperature in Fahrenheit is -31.7 °F.

Learn more about temperature here:

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#SPJ 4

Answer:

all cells are produced from other preexisting cells through cell division

A general exponential expression is something like:

A^n

This means that we need to multiply the number A by itself n times.

Using that we will get (-2)^6 = 64

With that definition, we can rewrite:

(-2)^6 = (-2)*(-2)*(-2)*(-2)*(-2)*(-2)

So we just need to solve the above expression.

Also, remember the rule of signs:

(-)*(-) = (+)

We will get:

(-2)*(-2)*(-2)*(-2)*(-2)*(-2) =  [(-2)*(-2)]*[(-2)*(-2)]*[(-2)*(-2)]

                                        =  4*4*4 = 16*4 = 64

Then we got:

(-2)^6 = 64

If you want to learn more, you can read:

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The reaction between boric acid and sodium hydroxide is an example of a weak acid strong base reaction.

Boric acid is a weak acid while sodium hydroxide is a strong base.

Having that in mind, we know that a weak acid dissociates only to a small extent in solution while a strong base is almost 100% ionized in solution.

It the follows that a lot of OH- will be left behind after the reaction since only a little fraction of it reacts with the H^+ from boric acid.

Hence, if equal moles of boric acid (H3BO3) and NaOH fully react, OH- is left in the solution after reaction.

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do you have the specific heat for part 2?

Answer: 24 kcal

Explanation:

Given

Mass of water [tex]m=0.3\ kg[/tex]

Temperature of water [tex]T_1=0^{\circ}[/tex]

Heat of fusion [tex]L_f=80\ cal/g[/tex]

Heat of vaporization [tex]L_v=540\ cal/g[/tex]

Specific heat of water [tex]c=1\ cal/g.^{\circ}C[/tex]

Heat require to melt the ice is

[tex]\Rightarrow Q=mL_f\\\Rightarrow Q=0.3\times 1000\times 80\\\Rightarrow Q=24000\ cal\ or\ 24\ kcal[/tex]

Thus, 24 kcal of heat is required to melt 0.3 kg of ice.

Answer:

C. Golden rice enriched with vitamin A

Answer:

THR ANSWER IS C) _ methylpropanoate

Answer:

a) E2

b) SN2

c) SN2

Explanation:

A substitution reaction involves replacement of an atom or group in a molecule by another atom or group. An elimination reaction is the loss of two atoms from the same molecule leading to the formation of a multiple bond in the molecule.

We must note that primary alkyl halides never undergo SN1/E1 reactions. However, the presence of a strong bulky base such as tert BuO- , E2 reactions predominate. In the presence of strong bases such as OH^- and good nucleophiles such as I^-, SN2 mechanism predominates.

Answer:

d) II and IV only.

Explanation:

A catalyst increases the kinetic energy of reactant molecules which increases the magnitude of collision. These then decreases the activation energy . A catalyst is not consumed by reaction because it is neither reactant nor a product, hence has no effect on equilibrium constant.

[tex].[/tex]

Answer:

A

Explanation:

it speed up a chemical reaction without being consumed by the reaction and increases the reaction rate by lowering the activation energy for a reaction but the average kinetic energy of the molecules remains the same well the required energy decreases

Answer:

Remove 1 electron

Explanation:

In the atom of each element, there are three subatomic particles viz: proton, neutron and electron. The number of proton (positively charged) and electron (negatively charged) determines the charge of that element. The more the proton, the more positively charged an ion is and vice versa for electron.

According to this question, a neutral atom of lithium (Li) with atomic no. 3 is given i.e. a lithium atom with charge 0. To make the lithium atom's charge change to +1, ONE ELECTRON MUST BE REMOVED OR LOST.

Note that, the proton number (atomic number) of an element does not change, rather the electron number changes in relation to the no. of protons.

Answer:

D. [CO₂]

Explanation:

Let's consider the following equation at equilibrium.

CaCO₃(s) ⇄ CaO(s) + CO₂(g)

The equilibrium constant, Kc, is the ratio of the equilibrium concentrations of products over the equilibrium concentrations of reactants each raised to the power of their stoichiometric coefficients. It only includes gases and aqueous species.

Kc = [CO₂]

A) the enthalpy of fusion

Explanation:

the heat of vaporization, is the amount of energy needed to change a liquid to a gas at constant temperature and pressure. The energy required to melt a solid to a liquid is called the heat of fusion,  and the heat of sublimation is the energy.

Answer:

A

Explanation:

Answer:

Robert Millikan was a physicist who discovered the elementary charge of an electron using the oil-drop experiment

Answer:

the mass of an electron using the Oil-Drop experiment.

Explanation:

Edit : OPTION C is the answer

Option B is the best, Even though the cost is 30 Billion it essentially takes Lesser time to construct. For Plan A, They would have to construct the overground railway and then take a lot of time and effort to create wildlife corridors and then plant trees. Plan B takes much less time compared to plan A and might as well have a lesser impact on the environment!

Answer:

An electrical conductivity meter (EC meter) measures the electrical conductivity in a solution. It has multiple applications in research and engineering, with common usage in hydroponics, aquaculture, aquaponics, and freshwater systems to monitor the amount of nutrients, salts or impurities in the water.

Answer:

phase transition from a solid to a gas

Explanation:

Entropy refers to the degree of disorderliness in a system. The more disorderly a system is, the greater the entropy of the system.

Decrease in the number of moles of a gas decreases the entropy of the system. Similarly, the entropy of solids is less than that of liquids. The entropy of liquids is less than that of gases.

Therefore, a change of phase from solid to gas represents an increase in entropy of the system.

Explanation:

chemical formula tells you the specific elements included in the compound and the number of atoms of each. The letters in a chemical formula are the symbols for the specific elements. So for example, H means hydrogen.

Explanation:

A chemical formula is a way of presenting information about the chemical properties of atoms that contribute a particular chemical compound or molecule, using chemical elements.

Answer:

Nombre de la siguiente estructura de compuesto orgánico

Explanation:

Answer:

0.034 M

Explanation:

1/[A] = kt + 1/[A]o

[A] = ?

k= 0.04556

t= 10.0 minutes or 600 seconds

[A]o = 0.50 M

1/[A] = (0.04556 × 600) + 1/0.50

[A] = 0.034 M