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Which of these is a characteristic of index fossils?

A- found in the topmost rock layer
B- found in many layers of the same rock
C- have already established relative age
D- are limited to a particular geological location

Renewable sources are which can be gained again and again from nature

for example : sun energy or wind energy

non renewable: these once consumed cannot be regained

example : fossil fuels

Now both can be used for many kinds of applications however the resources so we can say that Certain types of renewable energy can be used for as many applications as certain types of nonrenewable resources

Answer:

A.

Explanation:

The volume of one sodium atom with a metallic radius of 186 pm is [tex]\boxed{26965110.857\;{\text{p}}{{\text{m}}^3}}[/tex]

Further explanation:

The smallest particle that is the building block of matter is known as an atom. Most of the space in an atom is empty and its mass is concentrated inside a small region called the nucleus.

Protons, electrons, and neutrons are the three subatomic particles that are present in the atom. Electrons revolve around the nucleus in definite orbits.

The measure of the size of the atoms is known as its atomic radius or atomic size and is defined as the distance from the nucleus to the outermost shell that contains the electrons.  

Types of atomic radius:

1. Covalent radius

Half of the internuclear separation between the nuclei of the two single-bonded atoms of the same species is termed as a covalent radius.

2. Van der Waals radius

It is half of the distance between two unbonded atoms when these have balanced electrostatic forces of attraction.

3. Metallic radius

Half of the distance between the nuclei of two atoms in a crystal is called a metallic radius.

Consider the sodium atoms to be spherical. The formula to calculate the volume of spherical sodium atoms is as follows:

[tex]{\text{V}} = \frac{4}{3}{\pi }}{{\text{r}}^3}[/tex]                                                        …… (1)

Here,

V is the volume of sodium atoms.

r is the radius of the sodium atom.

The value of r is 186 pm.

Substitute this value in equation (1).

[tex]\begin{aligned}{\text{V}}&=\left( {\frac{4}{3}}\right) \times \left( {\frac{{22}}{7}} \right) \times {\left( {{\text{186 pm}}}\right)^3} \\&=\left( {\frac{{88}}{{21}}} \right) \times 6434856\;{\text{p}}{{\text{m}}^3} \\&=26965110.857\;{\text{p}}{{\text{m}}^3} \\ \end{aligned}[/tex]

Therefore, the volume of one sodium atom with a metallic radius of 186 pm is [tex]\boxed{26965110.857\;{\text{p}}{{\text{m}}^3}}[/tex]

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Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Solid State

Keywords: volume, sodium atom, 186 pm, radius, metallic radius, atomic radius, 26965110.857 pm3, atomic radius, covalent radius, van der Waals radius.

Dry ice and water ice are both forms of solid matter, thus, they share similar properties such as having a fixed shape and being incompressible. One of their notable shared attributes is their ability to undergo the process of sublimation.

Both dry ice (solid carbon dioxide, CO₂) and water ice are forms of solid matter, which means they are composed of atoms, molecules or ions and their particles are closely packed together. As a result, they share some physical properties. For instance, both dry ice and water ice have a fixed shape and are generally incompressible.

Both substances can also undergo sublimation which is a process where a substance transitions directly from a solid to a gas, bypassing the liquid state. For dry ice, it sublimes at room temperature and pressure, while water ice requires temperatures below its melting point to sublime. This process may be visible as mist or frost in the air.

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Answer: synthesis

Explanation:the answer given earlier does have a comment on it correcting but I missed that the first time I visited this question.

Answer: 25.5 L

Explanation:

According to avogadro's law, 1 mole of every substance occupies 22.4 Liters at STP and contains avogadro's number [tex]6.023\times 10^{23}[/tex] of particles.

We are given:

50.75 g of a gas occupies = 10.0 L at STP

Thus 129.3 g  of a gas occupies =[tex]\frac{10}{50.75}\times 129.3=25.5L[/tex] at STP

Thus 129.3 g of gas will occupy 25.5 L at STP.

The correct answer is sublimation.

help this helps :)

the answer is (#1) independent variable.

Answer:

oxygen

Explanation:

Always needed to combust

The radioactive isotopes used in studies of metabolic pathways, this is because their location of quantity can be experimentally determined because of their radioactivity.

A substance is called radioactive element if it changes its atomic number or atomic weight by releasing energy, this energy present as either Alpha, beta, or gamma forms of radiation.

The alpha is a Helium nucleus, a beta particle is an electron where as gamma is high energy electromagnetic radiation, the half life can be  defined as the time required by a radioactive substance to disintegrate  into a different substance.

If a radioactive element has a one-hour half-life, it means that half of the element will be decayed  and the remaining would decay within another hour.

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Final answer:

Astrology is a pseudoscience because it claims to be scientific but does not follow the scientific method, lacking falsifiable predictions and empirical verification, distinguishing it from legitimate sciences like astronomy.

Explanation:

Astrology is considered a pseudoscience because it is a belief system or practice that is often claimed to be scientific but does not adhere to a valid scientific methodology. It lacks the provision of falsifiable predictions or hypotheses, which is a core principle in the scientific method. Astrology, the practice of using celestial bodies to make predictions about human behaviors, positions itself as having an astronomical foundation, yet it does not engage in empirical and statistical methods that are characteristic of actual sciences like astronomy.

The correct answer to why astrology is a pseudoscience is B. it claims to be, but is not, a science. This is because astrology's methods do not incorporate the systematic observations, carefully-controlled experiments, and rigorous peer review that are the hallmarks of true scientific practice. While the movements and positions of celestial bodies (the subject of astronomy) can be precisely measured and predictions tested against observable outcomes, astrology (the supposed influence of celestial bodies on human life) does not operate within such testable frameworks.

The Law of Conservation of Matter applies to chemical reactions by stating that the amount and type of atoms in the reactants must equal the amount and type in the products. This is due to the fact that matter cannot be created or destroyed in an isolated system. For example, the reaction of hydrogen and oxygen to form water shows this conservation.

The Law of Conservation of Matter states that matter cannot be created or destroyed in an isolated system. In the context of chemical reactions, this means that the amount and type of atoms before the reaction (in the reactants) must be equal to the amount and type of atoms after the reaction (in the products).

For example, in the reaction of hydrogen and oxygen to form water: 2H2 + O2 -> 2H2O, there are 4 hydrogen atoms and 2 oxygen atoms both before and after the reaction. Thus, the total mass of the reactants equals the total mass of the products, illustrating the Law of Conservation of Matter.

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Chemists use substances with distinct physical and chemical properties to separate mixtures into individual substances. These can be pure substances (a single element or compound) or mixtures containing multiple substances. The specific composition of each substance or mixture determines its properties.

The substances that chemists use to separate mixtures into individual substances generally have distinct physical and chemical properties. Each compound has a specific composition and demonstrates definitive properties that make them unique from other compounds. These properties include elements such as physical properties like hardness and boiling point, and chemical properties like flammability and acidity.

Substances, in the form of elements and compounds, can be combined in many ways to form different mixtures. A mixture, which is commonly encountered in nature, contains two or more substances physically combined. The relative composition of a mixture plays a key role in determining its properties.

Pure substances consist of only one type of element or compound, while mixtures contain multiple. Pure substances include elements that cannot be further broken down by chemical changes. The known elements are just over 100, with around 90 naturally occurring on earth.

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If the internal energy of the products in a reaction is lower than the internal energy of the reactants, this means the reaction is an exothermic reaction and the sign of δe for the reaction is positive.

Internal energy is the property or state function which defines the energy of a substance in the absence of effects due to capillarity and the external electric, magnetic, and other fields.

In this reaction, the internal energy of products is lower than the internal energy of the reactants because the bonds in the products are stronger than those in the reactants, as a result the reaction releases more energy than it consumes. Therefore, the reaction is an example of exothermic reaction.

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Answer:

strontium, magnesium, calcium, beryllium

Explanation:

these all belong to the same group!

Strontium , magnesium,calcium and beryllium have similar  properties as they belong to same group.

In the periodic table, properties vary along  a  group as well as period due to the change in number of valence electrons. In a group the number of valence electrons remains same for all the elements of a group .

A new successive shell is added and hence number of valence electrons remain same.Number of valence electrons do not change in a group and hence elements in a group have similar properties as only valence electrons take part in chemical reactions.

While in a period, with each successive element one more electron is added to the same shell due to which number of valence electrons for each shell does not remain same,rather it increases with each successive element .As a result, of this elements in a period do not have similar properties.

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