Which of the following Is true about semi-conductors-neither free eletrons nor hoes are considered charge carriers in a semi-conductor
-exposing a crysal of a semiconductor to heat or light starts displacing valence electrons which then move throughout the crystal
-a material is classified as a semiconductor if its resistance to the flow of electric current is too low to permit it to be called a conductor

Answer : The correct option is, 0.200 g

Solution :

As we know that the radioactive decays follow first order kinetics.

First we have to calculate the rate constant of a samarium-146.

Formula used :

Putting value of in this formula, we get the rate constant.

Now we have to calculate the original amount of samarium-146.

The expression for rate law for first order kinetics is given by :

where,

k = rate constant  =

t = time taken for decay process  =

a = initial amount of the samarium-146 = 205 g

a - x = amount left after decay process  = ?

Putting values in above equation, we get the value of initial amount of samarium-146.

Therefore, the amount left of the samarium-146 is, 0.200 g

Ans: 0.200 g

Given:

Half life of Sm-146 = t1/2 = 103.5 million years

Time period, t = 1.035 billion years = 1035 million years

Original mass of sample, [A]₀ = 205 g

To determine:

Amount of sample after t = 1035 million years

Explanation:

The rate of radio active decay is given as:

A solution whose concentration of solute is equal to the maximum concentration that is predicted from the solute's solubility is called saturated solution.

What is solubility?

Solubility can be defined as a terminology that is used to describe how readily a chemical substance or compound can be dissolved in a solvent to form a solution.

In Science, a chemical substance or compound is said to be soluble if it dissolves completely in a solvent while it is insoluble if it doesn't dissolve or only dissolves partially.

In conclusion, a saturated solution refers to a solution whose concentration of solute is equal to the maximum concentration that is predicted from the solute's solubility.

Read more on solubility here: brainly.com/question/23946616

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

Further explanation

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

Learn more

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

The statement that accurately represents John Dalton’s model of the atom is

Further Explanation:

Postulates of John Dalton’s atomic model:

1. The matter contains indivisible particles. These particles are known as atoms.

2. Atoms can neither be created nor be destroyed.

3. Atoms of the same element show similarity in their shape and mass, but they are different from the elements of the other elements.

4. Atom is the smallest unit that participates in the chemical reaction.

5. Atoms of different elements can form compounds by combining with each other in a fixed, simple and whole number ratios.

6. Atoms of the same element can form two or more compounds by combining in more than one ratio.

Advantages of John Dalton’s atomic model:

1. This theory explains the laws of chemical combination.

2. It provides a clear distinction between atoms and molecules. Atom is the fundamental particle of an element whereas the molecule is that of a compound.

Limitations of John Dalton’s atomic model:

1. It failed to explain the further division of atoms into subatomic particles.

2. It did not mention any concept of isotopes (atoms of the same element with same atomic number and different mass numbers) and isobars (atoms of different elements with same mass number but different atomic numbers).

3. This theory failed to explain the reason for the existence of allotropes.

4. This theory is not applicable to complex organic molecules.

Dalton’s atomic model is also known as the billiard ball model. He assumed atoms to be tiny solid spherical objects similar to the billiard balls. He called these atoms as indivisible particles. But they have some mass for the particular element.

So atom is a tiny solid sphere with a predictable mass for the given element.

Learn more:

1. Rate of chemical reaction: brainly.com/question/1569924

2. Bohr’s model of the atom: brainly.com/question/2965079

Answer details:

Grade: High School

Subject: Chemistry

Chapter: Structure of the atom

Keywords: Tiny, solid, sphere, atom, John Dalton’s model, small particle, indivisible, allotropes, isobars, isotopes, complex, organic molecules, molecules, distinction, fundamental, laws of chemical combination, fixed, simple, chemical reaction.

Answer: option (3) SrO, with 84.56%

Explanation:

You have to calculate the mass of strontium and the mass of the compound, for each of the four compounds, and compute the percent:

percent of strontium = (mass of strontium / mass of the chemical formula) × 100 %.

These are the atomic masses of the elements that you have to use:

Atomic mass of Sr: 87.62 g/mol

Atomic mass of Cl: 35.453 g/mol

Atomic mass of I: 126.904 g/mol

Atomic mass of O: 15.999 g/mol

Atomic mass of S: 32.065 g/mol

(1) SrCl₂:

i) mass of Sr: 87.62 g/mol

ii) mass of Cl₂: 2×35.453 g/mol = 70.906 g/mol

iii) mass of SrCl₂: 87.62 g/mol + 70.906 g/mol = 158.526 g/mol

iv) Sr % = [87.62 / 158.526 ] × 100 = 55.27%

(2) SrI₂

Following the same procedure:

i) Sr % = [87.62 / (87.62 + 2× 126.904) ] × 100 = 25.66%

(3) SrO

i) Sr % = [87.62 / (87.62 + 15.999) ] × 100 = 84.56%

(4) SrS

i) Sr % = [87.62 / (87.62 + 32.065) ] × 100 = 73.21%

Answer:

the applied force is less than the force of friction.

Explanation: