Questions posted in Chemistry

A mol has several meanings: 1 mol of an atom, molecule or formula unit contains 6.022 x 10^23 atoms or the Avogadro's Number. Therefore, a formula unit is equal to a mole. Calculation of the formula units of magnesium chloride as follows;

11.4 g (1 mol/ 95.21 g) = 0.12 mol or formula unit

Answer:

The elements that have the same outer electronic configuration belong to the same group (column).

Explanation:

Periodic table is a form of classification of chemical elements. In this table, the elements are classified into seven rows and eighteen columns. The horizontal rows are called periods and the vertical columns are known as groups.

The chemical elements are arranged in the order of increasing atomic number. The elements that have the same outer electronic configuration belong to the same group. Whereas, the elements having the same number of shells belong to the same period.

The formula tells you the proportion in mols

2 mols of Cl: 1 mol of Pt

Now use the atomic masses:

Cl: 35.5 g/mol
Pt: 195 g/mol

Then you have these equation:

[2*35.5 g Cl] / 195 g Pt = x / 500 kg Pt

Solve for x.

x = (71 g Cl / 195 g Pt) * 500 kg Pt

x = 182 Kg Cl = 182 kg Cl2.

A is the right answer

there are 2parts of epidermis in a leaf upper epidermis and epidermis is the lower

Answer:High Pressure Low Temp would be the most efficient choice

Explanation:

In a dissolving process, energy is required to overcome the forces of attraction between the solvent particles. The first step is for the solvent particles to move in order for solute particles to enter the system. This process is endothermic where energy flows into the system. The second step is when solute particles must separate from other solute particles. Lastly, the solute should move between solvent particles.

The correct answer among the choices given is option A. Eustachian, Pharynx, Bronchi are structures that ensembles a tube. The Eustachian tube is a narrow passage from the pharynx to the middle ear. Pharynx is a passageway leading from the oral and nasal cavities to the larynx and the esophagus. Lastly, bronchi is an airway in the respiratory tract.

Answer:

In molecules of are 209 g

In molecules of are 123 g

In molecules of are 312 g

Explanation:

First remember that 1 mole of any element has molecules (this number is a constant).

we know that the molecular mass of an element relates the grams of that substance in 1 mol

To calculate how many grams of are in molecules we use a rule of three

The molecular mass of is 169.87 g/mol

In molecules of are 209 g

To calculate how many grams of are in molecules we repeat the previous procedure

The molecular mass of is 98.079 g/mol

In molecules of are 123 g

To calculate how many grams of are in molecules we repeat the previous procedure

The molecular mass of is 2 g/mol

In molecules of are 312 g

Answer : The number of moles present in 10.5 grams of NaCl are, 0.179 moles.

Solution : Given,

Mass of NaCl = 10.5 g

Molar mass NaCl = 58.5 g/mole

Formula used :

Now put all the given values in this formula, we get the moles of NaCl

Therefore, the number of moles present in 10.5 grams of NaCl are, 0.179 moles.

5.07x10^10 may be right but i dunoo know bro 

When ever I had to calculate changes in enthalpy I always used the equation q=mcΔT.

I hope this helps.  Let me know if anything is unclear.

A statement that accurately describes the dissolving process of a polar solute in water

C. Water molecules surround solute molecules.

Explanation:

By description, the "solvent" is the major composite and the "solute" is the lesser compound in solution. The roles/names may be modified if the compounds are commonly miscible. Water is an outstanding solvent because its polar water molecules makehydrogen bonds with ions and polar molecules, releasing ionic and polar covalent compounds to scatter easily in water.

Molar mass HBr = 80.91 g/mol

number of moles:

mass of solute / molar mass

52  / 80.91 => 0.642 mols

Volume = 0.25 L

M = n / V

M = 0.642 / 0.25

M = 2.568 mol/L

hope this helps!

Answer:

Given: Mass of books = 6.5 kg

Mass of CD's = 1.5 kg

Mass of DVD's = 2.0 kg

Total mass = 6.5 kg + 1.5 kg + 2.0 kg = 10 kg

The correct answer among the choices given is the last option. Increasing the surface area of the solute will increase the dissolution of a solute in the solvent. The dissolution rate is affected by a number of factors like temperature, pressure, particle size and the polarity.

Deforestation typically leads to soil erosion and the ruin of the ecosystem where deforestation occurred. The land gets destroyed and with it the natural habitat of the animals and plants who live there. In addition, we, the humans, lose oxygen because of lack of trees.

C. Chemical changes take place when a new substance is formed from an older substance. In this case, a new substance is formed when the magnesium metal is touched to a flame and the heat transforms it into the whitish, powdery substance.

It is named a solid,but i thin,k its metal but no its solid
...

Answer is: B) heavier than helium.

Helium (He) is an element with mass number 4 and carbon (C) is an element with mass number 12. Carbon has three time bigger mass numer, so new element is heavier thah helium.

For example, nuclear reaction: ²⁴⁹Cf + ¹²C → ²⁵⁷Rf + 4n°.

Californium-249 has mass number 259, carbon-12 has mass number 12 and rutherfordium-257 has mass number 257.

Mass number (A) is the total number of protons and neutrons in a nucleus.  

Sum of mass numbers of californium-249 and carbon-12 is 261 (249 + 12), but four neutrons are produced, so new element has mass number 257 (261 - 4).

The answer to the question is the option C. it cannot be physically broken down into different types of atoms. This means that the material is an element, which is a pure substance. Because an element is a pure substance that is formed by one only type of atoms. For example, gold is an element and all its atoms are of the same type. That is also true for any of the 118 elements of the periodic table. Compounds (other kind of pure substances) can be broken down into molecules (which contain different kind of atoms, but always in the same proportion) and mixtures (non pure substances) have different kind of substances.

Answer:

0.5 mol/yrs

hope this helps!

For [Ca +2 ]:
0.0010 mol/l · 0.05 l =
For [ SO4 -2 ] :
0.01 mol/l · 0.05 l = 
Cumulative volume:
 50 ml + 50 ml = 10 ml = 0.1 l
[Ca +2 ] =
[SO4 - 2] = 
Qc for CaSO4:
Qc =  
This is less than Ksp of CaSO4. 
 Answer: C ) No precipitation will occur.

Sulfur monoxide, I believe.

Changes at the rate of 3 or the third rate

Q=mcdeltaT
Q=400*4.18J/g*7
Q=11704J

The movement of particles within a solid is extremely slow when compared to that of a gas. It is also significantly slower in movement than that of the movement found within the particles of liquid. The more movement present and the faster the movement of the particles the more space will be present between each particle. This causes the material to spread out as they become less densely packed within a solid material.

Have electrons and the heavy particles at the same temperature, i.e. they are in thermal equilibrium with each other.

The chemical description of water is H2O, which means, it is composed of 2 hydrogen atoms and 1 oxygen atom. The answer to this item is the fourth option, " It is clear and colorless." When water is added with calcium, clear, colorless bubbles are formed. This explains a reaction of water with acid. The following are additional facts about water properties: Density: 1 g/cm³ Boiling point: 100 °C Molar mass: 18.01528 g/mol Melting point: 0 °C Formula: H2O

There are a lot of similarities between the two models.
Rutherford said that electrons revolve around the nucleus in rings.

Bohr also said it but in a slightly modified way.

He said that the orbits could have only certain fixed sizes depending on their allowed energies.

In an address to the Physical Society of Copenhagen, Bohr stated,

"It can be seen that it is impossible to employ Rutherford's atomic model so longas we confine ourselves exclusively to ordinary electrodynamics".

Bohr introduced the concept of electron shells.

Bohr did not prove that Rutherford was wrong. Rather, he improved and extended the Rutherford model.

There were two drawbacks to the Rutherford model.

It does not explain the hydrogen spectrum.It does not obey Maxwell's equations, which predict that an orbiting electron should fall into the nucleus.

Bohr's model is a defined, expanded model of Rutherford's atom that overcomes these two drawbacks.

The basics are the same, i.e., electrons revolve around the nucleus in paths called orbits with the nucleus at the centre.

Bohr expanded on Rutherford's model in detail.

The statement that describes a chemical property of water is this: IT REACT WITH SODIUM METAL.

Substances generally have two types of properties, these are chemical and physical properties. Physical properties of matters refer to those characteristics of matter which can be observed without changing the composition or nature of the matter. Examples of physical properties are color, boiling point, melting point, etc. Chemical properties on the other hand are those properties that can only be observed by changing the chemical nature of the substance. For instance, the chemical reaction of a substance with another substance will showcase the chemical properties of those substances.