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Answer:

In Niels Bohr's theory of the atom, electrons absorb and emit radiation of fixed wavelengths when jumping between fixed orbits around a nucleus. The theory provided a good description of the spectrum created by the hydrogen atom, but needed to be developed to suit more complicated atoms and molecules.

Explanation:

Answer:

ductile - germanium

mellabe - zirconium

Answer:

Check explanation section.

Explanation:

In order to understand balanced force and unbalanced forces the first law of Newton should be considered as a basic knowledge.

For Balanced forces, there is equal equality in the direction of the forces. In balanced forces, there is no acceleration.

For unbalanced forces, there is acceleration that is go say there is going to be movement. Therefore, net force is equal to unbalanced forces.

(i) Suitcase dropped from a height.

Answer: since there is movement that is acceleration, then the force here is unbalanced force. The resultant force is downwards.towards the greater force direction.

(ii) A bicycle moving with constant velocity on a straight road.

Answer: As the bicycle moves at constant velocity on the straight road the force here is Balanced. Frictional forces balances the forces from the cyclist.

(iii) The rope does not move in a tug of war on applying force at both ends.

Answer: Balanced force.

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Answer:

Here

Explanation:

Some assume our planet's changing distance from the sun causes the change in the seasons. That's logical, but not the case for Earth. Instead, Earth has seasons because our planet's axis of rotation is tilted at an angle of 23.5 degrees relative to our orbital plane, that is, the plane of Earth's orbit around the sun

Answer:

2.Diffusion

Explanation:

As we metabolize certain nutrients for the correct functioning of our cells, carbon dioxide is produced as a result. We need oxygen in order to metabolize them, so we need to have a system to incorporate it, and to eliminate the carbon dioxide produced.

This system is provided by the interaction between the respiratory system, which allows the enter of oxygen into the body and gets rid of the carbon dioxide, and the circulatory system, which acts transporting carbon dioxide and oxygen to and from the lungs, respectively.

The surface available for the gaseous exchange is enlarged by the pulmonary alveoli. The alveoli are the terminal aerial spaces of the respiratory system and the structures where the exchange between the air and blood is produced. Each alveolus is surrounded by a net of capillaries, where oxygen is freed from the hemoglobin and moves into the cells by diffusion. Carbon dioxide, diffuses out of the cells into the capillaries, where most of it dissolves in the plasma of the blood.

Josh is washing glasses with soap and water. He is afraid to carry the glasses because they are slippery. Josh could dry them with a towel to keep the glasses from being slippery.

Glasses are visual eyewear that have lenses fixed in a frame that holds them in front of a person's eyes. The frame often has a bridge over the nose and arms that rest over the ears. Glasses are also known as eyeglasses or spectacles.

The term "glasses" likely originated from the word "spyglass," which was originally used to describe "a pair of eyeglasses" that had to be held up to the eyes in order to be fully effective.

Eyeglasses, often known as glasses or spectacles, are lenses that are mounted in frames and worn in front of the eyes to improve vision or to correct astigmatism, myopia, or hyperopia.

Thus,  Josh could dry them with a towel to keep the glasses from being slippery.

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Answer:

0.007 mol

Explanation:

Step 1: Given data

Volume of acetaminophen: 0.8 mL

Step 2: Calculate the mass corresponding to 0.8 mL of acetaminophen

The density of acetaminophen is 1.26 g/mL.

0.8 mL × (1.26 g/mL) = 1 g

Step 3: Calculate the number of moles corresponding to 1 g of acetaminophen

The molar mass of acetaminophen is 151.16 g/mol.

1 g × (1 mol/151.16 g) = 0.007 mol

Answer:

1)conduction

2) convection

3) conduction

4) radiation

5) radiation

6) radiation

7) conduction

8) conduction

9) radiation

10) convection

Explanation:

not 100% sure

Answer:

6 days

Explanation:

The following data were obtained from the question:

Original amount (N₀) = 100 mg

Amount remaining (N) = 6. 25 mg

Time (t) = 24 days

Half life (t½) =?

Next, we shall determine the decay constant. This can be obtained as follow:

Original amount (N₀) = 100 mg

Amount remaining (N) = 6. 25 mg

Time (t) = 24 days

Decay constant (K) =?

Log (N₀/N) = kt / 2.303

Log (100/6.25) = k × 24 / 2.303

Log 16 = k × 24 / 2.303

1.2041 = k × 24 / 2.303

Cross multiply

k × 24 = 1.2041 × 2.303

Divide both side by 24

K = (1.2041 × 2.303) / 24

K = 0.1155 /day

Finally, we shall determine the half-life of the isotope as follow:

Decay constant (K) = 0.1155 /day

Half life (t½) =?

t½ = 0.693 / K

t½ = 0.693 / 0.1155

t½ = 6 days

Therefore, the half-life of the isotope is 6 days

Given the balanced equation:

( Reaction type : double replacement)

CaF2 + H2SO4 → CaSO4 + 2HFI

We can determine the number of grams prepared from the quantity of 75.0 H2SO4, and 63.0g of CaF2 by converting these grams to moles per substance.

This can be done by evaluating the atomic mass of each element of the substance, and totaling it to find the molecular mass.

For H2SO4 or hydrogen sulfate it's molecular mass is the sum of the quantity of atomic mass per element. H×2 + S×1 + O×4 = ≈1.01×2 + ≈32.06×1 + ≈16×4 = 2.02 + 32.06 + 64 = 98.08 u (Dalton's or Da) or g / mol.

For CaF2 or calcium fluoride, it's molecular mass adds 1 atomic mass of calcium and 2 atomic masses of fluoride due to the number of atoms.

Ca×1 + F×2 = ≈40.07×1 + ≈19×2 = 40.08 + 38 = 78.07 u (Da or Dalton's) or g / mol.

The limiting  reactant in the given balanced reaction is sulphuric acid. The mass of HF produced from 75 g of H₂SO₄ is 30 g.

The limiting reactant in a species is the reactant which is fewer in amount and thus determine the yield of the product.

In the given reaction, one mole of calcium fluoride reacts with one mole of sulphuric acid to give two moles of HF. The molar mass of calcium fluoride CaF₂ is 78 g/mol the weight taken here is 63 g. Thus number of moles is 63/78 = 0.87 moles.

The molar mass of sulphuric acid H₂SO₄ is 100g/mol. The weight taken here is 75 g and thus, number of moles is 75/100 = 0.75 moles. One mole of calcium fluoride need one mole of H₂SO₄ . Thus 0.87 neede 0.87 moles of H₂SO₄ . But here we have only 0.75. Thus it is the limiting reactant.

As per the reaction, one mole or 100 g of H₂SO₄  produce 2 moles or 40 g of HF (molar mass = 20 g/mol). Thus mass of HF produced from 75 g is calculated as follows:

mass of HF = (75 × 40)/100

                   =  30 g.

Hence, mass of HF produced in this reaction is 30 g.

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Hello there!

Your answer is C.

Answer:

The right option is; A. It is younger than the rock layer below.

Explanation:

A rock layer deposited on top of another rock layer is younger than the rock layer below. This is based on the law of superposition which states that in any undeformed sequence of rocks that are laid down in layers, the youngest layer of rock will be on top of the sequence, while the oldest layer will be at the bottom of the sequence.

Answer & Explanation:

Susana's red crystal sample is a compound because it was broken down into a gas and blue powder. It is not an element because elements cannot be broken down into simpler substances by ordinary means, such as heating.

Answer:

Susana's red crystal sample is a compound because it was broken down into a gas and blue powder. It is not an element because elements cannot be broken down into simpler substances by ordinary means, such as heating.

Explanation

Sample response form Edg

Answer:

I think it is D.

Explanation:

Answer:

b

Explanation:

Answer:

false

Explanation:

Weathering describes the breaking down or dissolving of rocks and minerals on the surface of the Earth. Water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering.