why is an element considered a pure substance​

Answer:

The answer is the same as .

Explanation:

There are 3 atoms in NaOH, 1 sodium, 1 oxygen and 1 hydrogen.

There are 3 atoms in H2O, 2 hydrogen and 1 oxygen.

There are two types of ions in chemistry, one is cation and the other is anion. Anion is the negative charge ion. Therefore, the formula of hydrogen sulfite ion is HSO₃⁻

Chemical Compound is a combination of ions, ions forms by combination of element and element forms by combination of atoms in fixed proportion.

According to our question the chemical compound from which hydrogen sulfite ion is coming is sulfurous acid that is H₂SO₃. So to get hydrogen sulfite ion we need to remove one hydrogen ion that is H⁺ from the chemical compound sulfurous acid.

The balanced reaction is

H₂SO₃[tex]\rightarrow[/tex]H⁺ + HSO₃⁻

From above reaction we can see that the charge over hydrogen sulfite ion is -1

Therefore the formula of hydrogen sulfite is HSO3-

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the molar concentration should be atleast 5mL off the solution since its disolved

Answer:

8.3

Explanation:

Convert mL to L.

12 mL×1 L1000 mL=0.012 L

Solve for molarity.

Molarity=moles of solute

liters of solution=0.10 mol0.012 L=8.3 M

Answer:

Option C.

Explanation:

The arrangement of electrons in their orbital follows certain rules.

The Hund's rule practically explained how electrons are distributed in their orbitals.

The Hund's rule states that electrons distributed among the orbitals of the same shell singly (without partner) before pairing occurs.

In the filling of these electrons in their orbitals, we fill in the electron without pairing first because electrons tends to repel each other before filling with the opposite spin as shown in the attached photo.

Explanation:

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Answer:

Explanation:

Start by writing water as HOH

Ca(OH)2 +CO2 = CaCO3+ HOH

Next pay attention to the CO2 going to CO3

We need an oxygen.

Fortunately that is provided by the (OH)2

Now we have

Ca(OH)2 + CO2 ==> CaCO3 + HOH

and believe it or not, that is balanced as it is

The left side has 1 Ca. So does the right side

The Left side has 1 C.  So does the right side.

The left side has 2 H. So does the right side

The left side has 2 oxygens (in Ca(OH2)) + 2 oxygens in CO2

So the equation is balanced.

Answer:

The second law of thermodynamics states that the total entropy of an isolated system can never decrease over time, and is constant if and only if all processes are reversible.

Explanation:

Isolated systems spontaneously evolve towards thermodynamic equilibrium, the state with maximum entropy. hope this helps you :)

The second law of thermodynamics say about entropy The entropy in a system and its surroundings tends to increase.

According to the second law of thermodynamics, Entropy of the universe keeps on increasing overtime. When the entropy decreases and enthalpy increases the free energy change,  ΔG, is positive and not spontaneous, and it does not matter what the temperature of the system is. Temperature comes into play when the entropy and enthalpy both increase or both decrease. The reaction is not spontaneous when both entropy and enthalpy are positive and at low temperatures, and the reaction is spontaneous when both entropy and enthalpy are positive and at high temperatures. The reactions are spontaneous when the entropy and enthalpy are negative at low temperatures, and the reaction is not spontaneous when the entropy and enthalpy are negative at high temperatures.

Therefore, The second law of thermodynamics say about entropy The entropy in a system and its surroundings tends to increase.

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Answer:

composition of soda-lime glass is 73% SiO2 – 15% Na2O − 7% CaO − 4% MgO − 1% Al2O3 [129,132,133].

The Soda glass formula is SiO2, Na2O, CaO, Al2O3, K2O, SO3, MgO, Fe2O3, TiO2

Soda glass is a chemical compound that stands out for being the most widely used material to make windows, bottles, glasses, among others.

This compound is characterized by being chemically stable, reasonably hard, and extremely versatile because it can be recycled since it can be melted to make new products.

Its chemical formula is made up of other compounds such as:

Additionally, the compounds found in the highest proportion in glass are SiO2 (74 atoms) and Na2O (13 atoms).

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Answer:

true

Explanation:

The standard laboratory rule is to always add acids or bases to solvent and not the other way round.

The dissolution of concentrated acids/bases in solvents (water) generates heat energy. Thus, if the solvent is added to them, a layer of hot weak acid or base will be formed and this will boil and spray around, causing an explosion.

On the other hand, if acid/base is added to solvents, they flow into the solvents and get diluted immediately without any boiling taking place. Hence, it is safe to add acid/base to solvents and not the other way round.

Answer:

0.35 g.

Explanation:

We'll begin by calculating the number of mole of Fe(NO3)3 in 35 mL of 0.250 M Fe(NO3)3 solution.

This is illustrated below:

Molarity of Fe(NO3)3 = 0.250 M

Volume = 35 mL = 35/1000 = 0.035 L

Mole of Fe(NO3)3 =?

Molarity = mole /Volume

0.250 = mole of Fe(NO3)3 / 0.035

Cross multiply

Mole of Fe(NO3)3 = 0.25 x 0.035

Mole of Fe(NO3)3 = 8.75×10¯³ mole

Next, we shall determine the number of mole of KOH in 55 mL of 0.180 M

KOH solution. This is illustrated below:

Molarity of KOH = 0.180 M

Volume = 55 mL = 55/1000 = 0.055 L

Mole of KOH =.?

Molarity = mole /Volume

0.180 = mole of KOH /0.055

Cross multiply

Mole of KOH = 0.180 x 0.055

Mole of KOH = 9.9×10¯³ mole.

Next, we shall write the balanced equation for the reaction. This is given below:

3KOH + Fe(NO3)3 —> Fe(OH)3 + 3KNO3

From the balanced equation above,

3 moles of KOH reacted with 1 mole of Fe(NO3)3 to produce 1 mole of Fe(OH)3.

Next, we shall determine the limiting reactant. This can be obtained as follow:

From the balanced equation above,

3 moles of KOH reacted with 1 mole of Fe(NO3)3.

Therefore, 9.9×10¯³ mole of KOH will react with = (9.9×10¯³ x 1)/3 = 3.3×10¯³ mole of Fe(NO3)3.

From the above illustration, we can see that only 3.3×10¯³ mole out of 8.75×10¯³ mole of Fe(NO3)3 given is needed to react completely with 9.9×10¯³ mole of KOH.

Therefore, KOH is the limiting reactant and Fe(NO3)3 is the excess reactant.

Next, we shall determine the number of mole of Fe(OH)3 produced from the reaction.

In this case, we shall use the limiting reactant because it will give the maximum yield of Fe(OH)3 as all of it is consumed in the reaction.

The limiting reactant is KOH and the mole of Fe(OH)3 produce can be obtained as follow:

From the balanced equation above,

3 moles of KOH reacted to produce 1 mole of Fe(OH)3.

Therefore, 9.9×10¯³ mole of KOH will react to produce = (9.9×10¯³ x 1)/3 = 3.3×10¯³ mole of Fe(OH)3.

Finally, we shall convert 3.3×10¯³ mole of Fe(OH)3 to grams. This can be obtained as follow:

Molar mass of Fe(OH)3 = 56 + 3(16 + 1) = 56 + 3(17) = 107 g/mol

Mole of Fe(OH)3 = 3.3×10¯³ mole

Mass of Fe(OH)3 =?

Mole = mass /Molar mass

3.3×10¯³ = Mass of Fe(OH)3 / 107

Cross multiply

Mass of Fe(OH)3 = 3.3×10¯³ x 107

Mass of Fe(OH)3 = 0.3531 ≈ 0.35 g.

Therefore, 0.35 g of Fe(OH)3 was produced from the reaction.

Answer:

C. the same amount of energy as

Explanation:

Firstly, a chemical reaction can either absorb energy from its surroundings to occur or release energy into its surroundings as a product. The former and latter descriptions are called ENDOTHERMIC and EXOTHERMIC reactions respectively. An exothermic reaction is that which transfers energy, in form of heat, to its surroundings while an Endothermic reaction is that which absorbs energy (heat) from its surroundings.

However, a reversible reaction is that reaction in which the formation of products from reactants and reformation of the reactants from products occur simultaneously. Hence, the products of a reversible reaction can become the reactants and move in the opposite direction. For example:

Reversible reaction: A + B ⇆ C + D means;

A + B → C + D and;

C + D → A + B

In a case whereby the opposite reactions consist of an endothermic and exothermic reactions, the endothermic reaction absorbs the same amount of energy as the exothermic reaction releases.

According to the law of conservation of energy, no energy is lost during a reversible reaction. Hence, in order to achieve an equilibrium, the amount of energy absorbed by the endothermic reaction is the same as the amount of energy released in the opposite exothermic reaction.

a single neutral atom of zinc has 30 protons

Answer:

The correct option is;

The gas particles move faster, have the same molecular composition, and have weaker attractions between them than the liquid particles

Explanation:

The properties of the gas molecules in comparison to liquids are

1) The gas molecules are widely spread out

2) After evaporation and while in conditions favorable to the gaseous state, the kinetic energy of a gas is larger than the inter molecular attractive forces

3) A gas fills the container in which it is placed

For liquids

1) There are strong intermolecular forces holding the molecules together in a liquid

2) Liquid attractive forces in a liquid are strong enough to hold neighboring molecules

3) The volume of a liquid is definite.

Answer:

The particles of frosting absorbed energy from their surroundings and changed from the solid to the liquid state.

Explanation:

On a sunny day, the energy of the particles in the surrounding is higher than the energy of the frosting tray of cupcakes.

As a result of the exchange of energy between the tray of cupcakes and the surrounding, the tray of cupcakes absorbs energy from the surrounding. When this occurs, the firm frosting is now converted from solid to liquid which is runny and wet to touch, hence the answer above.

Answer:

D. Zinc.

Explanation:

Galvanization is a metal-coating process which involves the application of a thin layer of zinc to an iron or steel, so as to prevent rusting or corrosion.

The zinc metal protects the iron from rusting by sealing the surface of the iron and thus, preventing weathering and oxidation.

Hence, if Mike wants to galvanize iron to protect it from rusting. The metal he should use is zinc (Zn) because a coating of zinc would protect the iron (Fe) by corroding first when exposed to moisture or the atmosphere.

Answer:

b

Explanation:

Answer:

C. 1 cubic foot of loose sand

Explanation:

For many  objects having equal volume , surface area will be maximum

of the object which has spherical shape .

But when a sphere is broken into tiny small spheres , total surface area of all the small spheres will be more than surface area of big sphere .

Hence among the given option , surface area of loose sand will have greatest surface area . Loose sand is equivalent to small spheres .

Answer:

the answer would be C 1 cubic foot of loose sand.

Answer is D

Explanation:

Answer:

B. Neutral

Explanation:

When there is a ionic bond,  one element steals or takes away an electron from the other element.

An example is NaCl

In this compound, Chlorine atom steals an extra electron from Sodium to fill its outer shell. So, this is a Ionic bond. Since, the Sodium compound gives away an atom, it is positively charged. Since, Chlorine steals an atom, it is negatively charged. Opposite charges attract, so they become a compound.

When positive and negative mix, it becomes neutral.

Answer:

[tex]\Large \boxed{\mathrm{A}}[/tex]

Explanation:

Rust formed from iron and oxygen combining is a chemical change, because in a chemical change, the resulting substance(s) will have different properties from the substance(s) before the chemical change.

I cant comment... So is it Right?

Answer: D. False, it should read, "A theory and a law are already both supported by evidence and are equal, but they have different functions."

Explanation:

A  "Theory" and  a'' Law" in scientific method are already both supported by evidence but they have different function,

The function of  " Theory" in scientific method is to give an explanation to the observations and findings gathered during the process. It can be modified, improved or even rejected as more information is being gathered.

While a '' Law '' tends to describe an observed event in nature that is true whenever it is put to test. It does not explain why the occurence or event is true.

Answer:

inter atomic bonds

Explanation:

because it is loosely held

Answer:

The Conservation area is the pay way to the special architectural and historic interest  these are special character.

Explanation:

Conservation area is the features of building and use that historical development to contribute to its special character material and style.

Answer:

88

Explanation:

The ion has a charge of 2+, therefore the number of neutrons it possess is 86+2

which equals 88

The element X having a mass number of 230 and has 86 electrons is radium and has  142 neutrons.

An atom is composed basically of electrons, protons and neutrons. In a neutral atom, the number of protons and electrons are equal. The number of neutrons is the difference between the mass number and the number of protons (atomic number).

Since we know that the ion of the element X has 86 electrons and the compound formed is XBr2, it then means that neutral X has 88 electrons.

The number of electrons in the neutral atom is the same as the number of protons or atomic number. An element can be identified by its atomic number. The element having atomic number 88 is radium.

The number of neutrons is obtained as;

Mass number - atomic number

230 - 88 = 142 neutrons

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Answer:

1. Metal.

2. Atom.

3. Homogeneous

4. Compounds.

5. Lustrous

6. Saturated.

7. Colloidal; true.

8. Homogeneous.

Explanation:

1. An element which are sonorous are called metal.

2. An element is made up of only one kind of atom.

3. Alloys are homogeneous mixtures.

4. Elements chemically combines in fixed proportion to form compounds.

5. Metals are lustrous and can be polished.

6. A solution in which no more solute can be dissolved is called a saturated solution.

7. Milk is a colloidal solution but vinegar is a true solution.

8. A solution is a homogeneous mixture.

Answer:

1) The volume occupied by an atom is composed of mainly empty space

2) Atoms have a very small, relatively dense, central nucleus that is positively charged

3) The region around the nucleus of an atom are orbited by negatively charged electrons in a the same fashion planets orbit around the Sun.

Explanation:

The selection of gold for the gold foil experiment was due to its ability to be rolled into extremely thin sheets such that it was expected for alpha particle to perforate or pass through the foil.

Answer:

FADH2 has a lower (less negative) redox potential than NADH does

Explanation:

Flavin Adenine Dinucleotide (FAD) and Nicotinamide Adenine Dinucleotide (NAD) are redox cofactors that play important functions for mitochondrial activity and cellular redox balance. Both coenzymes exist in two forms: an oxidized and a reduced, which are abbreviated as NAD/FAD and NADH/FADH2, respectively. These reduced forms (NADH and FADH2) are produced in the Krebs cycle during respiration. FADH2 has lower redox potential than NADH because FADH2 is only capable of activating 2 proton pumps, while NADH can activate 3 proton pumps during the electron transport chain, thereby FADH2 generates a minor number of ATP molecules than NADH.

Answer:

The water cycle or hydrologic is a continuous cycle where water evaporates, travels into the air and becomes part of a cloud, falls down to earth as precipitation, and then evaporates again. This repeats again and again in a never-ending cycle. Water keeps moving and changing from a solid to a liquid to a gas, over and over again.

Precipitation creates runoff that travels over the ground surface and helps to fill lakes and rivers. It also percolates or moves downward through openings in the soil to replenish aquifers under the ground. Some places receive more precipitation than others do. These areas are usually close to oceans or large bodies of water that allow more water to evaporate and form clouds. Other areas receive less precipitation. Often these areas are far from water or near mountains. As clouds move up and over mountains, the water vapor condenses to form precipitation and freezes. Snow falls on the peaks.

The continual movement of water on, above, and below the Earth's surface is referred to as the water cycle, also known as the hydrological cycle.

The water cycle demonstrates how water is constantly moving both inside the Earth and in the atmosphere. It is a complicated system with a wide range of processes.

Water vapor is created when liquid water evaporates, and this water vapor then condenses to form clouds and falls back to earth as rain and snow.

The constant flow of water between the ground and the atmosphere is known as the water cycle. Water travels to land as precipitation, like snow and rain.

The cycle is then completed by the water evaporating, condensing into clouds in the atmosphere, and precipitating once more on earth. The water cycle is composed mostly of four processes: evaporation, convection, precipitation, and collection.

Thus, The continual movement of water on, above, and below the Earth's surface is referred to as the water cycle.

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Answer:

The volume at 0.860 atm and 15°C will be 56.638 L

Explanation:

Gay Lussac's law explains the variation in the pressure of a gas by modifying its temperature, keeping the volume constant: it determines that pressure and temperature are directly proportional quantities. In other words, Gay-Lussac's law states that when a gas undergoes a constant volume transformation, the ratio of the pressure exerted by the temperature of the gas remains constant:

[tex]\frac{P}{T}=k[/tex]

On the other hand, Boyle's law determines that the pressure exerted by a gas is inversely proportional to its volume at constant temperature. This is expressed mathematically as:

P*V=k

Finally, Charles's law says that at constant pressure, the volume of an ideal gas is directly proportional to its absolute temperature and is expressed mathematically as:

[tex]\frac{V}{T}=k[/tex]

Combined law equation is the combination of three gas laws called Boyle's, Charles's and Gay-Lussac's law:

[tex]\frac{P*V}{T}=k[/tex]

When you want to study two different states, an initial one and a final one of a gas, you use:

[tex]\frac{P1*V1}{T1}=\frac{P2*V2}{T2}[/tex]

In this case:

Replacing:

[tex]\frac{1.05 atm*48 L}{298 K}=\frac{0.86atm*V2}{288 K}[/tex]

and solving:

[tex]V2=\frac{288 K}{0.86 atm} *\frac{1.05 atm*48 L}{298 K}[/tex]

you get:

V2= 56.638 L

The volume at 0.860 atm and 15°C will be 56.638 L

Answer:

using a more concentrated potassium hydroxide

Explanation:

The option that would likely increase the rate of reaction would be to use a more concentrated potassium hydroxide.

The concentration of reactants is one of the factors that affect the rate of reaction. The more the concentration of the reactants, the faster the rate of reaction.

Granted that there are enough of the other reactants, increasing the concentration of one of the reactants will lead to an increased rate of reaction.

Hence, using a more concentrated potassium hydroxide which happens to be one of the reactants would likely increase the rate of reaction.

Answer:

using a more concentrated potassium hydroxide

Explanation: