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3 years ago

Which of the following reactions is spontaneous?

1 answer:

5 0

Answer is: lumps os sugar dissolving in water.
Sugar has very good solubility in water and it dissolves readily, which is example of a physical change.
Gibbs free energy (G) determines if reaction will proceed spontaneously, if ΔG is negative, reaction is spontaneous (ΔG = ΔH - T·ΔS).
In other examples, reactions are spontaneous in reverse way, for example spontaneous is forming sodium chlorine from sodium metal and chlorine gas, but not sodium chloride forming sodium metal and chlorine gas, because a lot of energy is needed for that reaction.

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PLEASE ANSWER Which is/are true?

Alona [7]

You have to check each statement, so this is equivalent to 5 different questions.

Answers:

The true statements are:

b. Si has valence electrons in the n = 3 energy level.

d. Xe has valence electrons in the n = 5 energy level.

Explanations:

a. Li has valence electrons in the n = 1 energy level.

Answer: False.

Valence electrons are the electrons in the outermost main energy level (shell of electrons).

To determine where the valence electrons are, you build the electron configuration, using Aufbau rules to predict the orbital filling: in increasing order of energy.

The atomic number of lithium (Li) is 3. Hence, you have to distribute 3 electrons, and so its electron confiuration is:

1s² 2s¹

The only valence electron is in the 2s orbital, i.e. in the n = 2 energy level.

b. Si has valence electrons in the n = 3 energy level.

Answer: True

Silicon (Si) has atomic number 14, so you have to distribute 14 electrons in increasing order of energy:

1s² 2s² 2p⁶ 3s² 3p²

Thus, Si has five valence electrons, and they are in the n = 3 energy level.

c. Ga has valence electrons in the n = 3 energy level.

Answer: False

Gallium has atomic number 31, so you have to distribute 31 electrons, filling the orbitals in increasing order of enery.

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p¹

The highest energy level is 4. This is where the valence electrons are. So, Ga has the valence electrons in the n = 4 level (not n = 3 as the statement describes).

d. Xe has valence electrons in the n = 5 energy level.

Answer: True

The atomic number of Xe is 54.

Using the short notation (noble gas notation), and filling the orbitals in increasing order of energy, you get the configuration:

[Kr] 5s² 4d¹⁰ 5p⁶.

Hence, the valence electrons are in the n ) 5 level, such as the statement describes.

e. P has valence electrons in the n = 2 energy level.

Answer: False

Phosphorus (P) has atomic number 15, hence there are 15 electrons.

The electron configuration following the increasing order of energy, which you can remember using Aufbau rules, is:

1s² 2s² 3s² 3p³

Then, the valence electrons are in the n = 3 energy level; not in the n = 2 energy level.

3 0

3 years ago

How surface area affects the rate of a reaction.

alexandr402 [8]

The smaller the surface area, the faster the rate of reaction will be. Think of ice. A full sized ice cube will take longer to melt than crushed ice. Crushed ice will melt much quicker because there is more surface area exposed. So if the surface area can be increased, so will the rate of reaction.

Hope this helps! :)

8 0

3 years ago

As a "rule of thumb" there are 20 drops of a liquid in a mL. Using this estimate and a density of 1.685, how many moles are in 2

arlik [135]

Answer:

0.020 mol

Explanation:

Let's consider the following relations:

20 drops of a liquid have a volume of 1 mL.
The density of the solution is 1.685 g/mL, that is, each milliliter of solution has a mass of 1.685 g of solution.
There are 85 g of phosphoric acid per 100 grams of solution (85 % by weight).
The molar mass of phosphoric acid is 97.99 g/mol

With these relations, we can calculate the moles of phosphoric acid in 27 drops of solution.

$27drop \times \frac{1mL}{20drop} \times \frac{1.685gSolution}{1mL} \times \frac{85gH_3PO_4}{100gSolution} \times \frac{1molH_3PO_4}{97.99gH_3PO_4} = 0.020 mol$

4 0

3 years ago

The idea that atoms are indivisible explains all of the following except which of the following

Crazy boy [7]

Answer:

ll matter is composed of extremely small particles called atoms.

Atoms of a given element are identical in size, mass, and other properties. Atoms of different elements differ in size, mass, and other properties.

Atoms cannot be subdivided, created, or destroyed.

Atoms of different elements can combine in simple whole number ratios to form chemical compounds.

In chemical reactions, atoms are combined, separated, or rearranged.

Each atom is uniform, homogeneous, colorless, tasteless, and indivisible.ll atoms of a given element are identical in mass and properties. Compounds are formed by a combination of two or more different kinds of atoms. A chemical reaction is a rearrangement of atom.

5 0

3 years ago

What happens when the pressure of gas is lowered

Svet_ta [14]

Answer:

its volume will increase

8 0

2 years ago