21. If you have 350 milliliters (mL) of a 500-milligramper liter (mg/L) solution of alum (aluminum sulfate),how much water would you have to add to bring theconcentration down to 100 mg/L? Assume that youare adding water that does not contain any alum (C2=0).1. 70 mL2. 1,400 mL3. 143 mL4. 1,750 mL

An atom is stable when its total charge is equal to 0 (zero).

There are 2 situacions that can make an atom not stable (or its total charge is not zero):

1. One situation is that the atom has excess of negative charge. In this case, the atom is stabilized by transferring valence electrons to another atom.

2. Another situation is that the atom has excess of positive charge. In this case, the atom is stabilized by obtaining electrons from another atom.

In both cases, the parts of the atom related to the stable state are the electrons.

Step 1

Water is supposed to be in the gas phase and it is assumed that it is an ideal gas.

Therefore, it can be applied:

p x V = n x R x T (1)

p = pressure = 6.32 atm

V = volume = 39.2 L

n = moles = unknown

R = gas constant = 0.082 atm L/mol K

T = absolute temperature = 486 °C + 273 = 759 K

-------------------

Step 2

n is cleared from (1):

p x V/R x T = n

(6.32 atm x 39.2 L)/(0.082 atm L/mol K x 759 K) = n

3.98 moles = n

Answer: number of moles = 3.98 moles

a)

Hydrochloric acid: HCl

Sodium hydroxide: NaOH

In the neutralization, an acid and a base react to neutralize the H⁺ and OH⁻, forming water.

In a displacement reaction, an atom in one of the components is displaced to another component in the reaction.

In the case of HCl and NaOH, we can see this as a double displacement, where H⁺ from HCl is exchanged by the Na⁺ of the NaOH, forming NaCl and H₂O:

b)

Acetic acid: CH₃COOH

Sodium hydrocide: NaOH

In this case, the NaOH is the same. the Aceitc acid dissociates in the following way:

So, we just need to visualize the CH₃COO⁻ as the Cl⁻ of item a.

That is, we will have the reaction exchanging H⁺ and Na

Answer:

D. 16.5 moles

Explanation:

From the balanced reaction we know that 1 mole of Zn reacts with 2 moles of HCl.

We can calculate the moles of HCl needed to react completely with 8.25 moles of zinc, using the stoichiometry of the reaction and a mathematical rule of three:

So, 16.5 moles of HCl are needed.

Explanation:

We determine the mass of NO2 from the mass of Pb(NO3)2:

m is the mass, M is the molar mass

Percent yield:

Answer:

Percent yield = 95.86%

Answer

C. table salt (sodium chloride) in water

Explanation

Sodium chloride dissolves in water forming a solution

Remembering the formula of density, we can clear the volume and replace the given data in the new formula:

Our data is: for mass is 17.7 grams (g) and for density is 0.727 g/mL:

The volume of the ether is 24.3 mL of 17.7g and 0.727 g/mL.

We are given two volume values, each volume has a certain number of molecules. The second number 6.20 x10^23 corresponds to the avogadro number and is equivalent to one mole of silicon. The first number does not make a molecule, so it must be only a fraction of the molecule of silicon being measured.

That will be the diference between the two number. 6.20 x10^23 is equivalent to one molecule while 4.188x10^22 is not.

In nature it is possible to find aqueous solutions of salts in both basic and acidic forms, for the basic salts, which can also be called Alkali salts, we have a few, for example, Sodium carbonate, Sodium sulfide, Sodium hydroxide. For the acidic salts we can have NaHSO4, Sodium bisulfate. Therefore this is a false statement.

So,

We could use the Charles law:

In this case, we have:

V1=122ml

T1=25°C

V2=50ml

T2=?

Let's replace these values in the equation in order to find T2:

The final temperature is about 10.2459°C.

Fractional uncertainty is found by dividing the absolute uncertainty by the quantity itself. It is always the same for every measure: mass, volume, density, etc.

For example, if we have this measure 7.5+-0.1kg. The fractional uncertainty is:

In this question we have the concept of solutions and mixtures, let's analyze each option in order to find the one that best fits with reality:

A. Heterogeneous mixtures and solutions aren't the same thing, a mixture is when you have two or more compounds mixed together in a container, and a mixture can be heteregenous (which will form two or more phases), or homogeneous (which will be uniform throughout the mixture), and a solution will be the same as a homogeneous mixture.

B. A pure substance will not be separated by any method, since there is nothing the separate, it is all the same substance

C. As I said in letter A, a heteregeneous mixture will not have the same phase, but it will have different phases

D. The composition of a homogeneous mixture will be uniform, just a as a solution

The correct one will be letter D

25.81%

The formula for calculating the percent volume/volume of a solution is given as:

Given the following parameters

volume of solute (methanol) = 80mL

volume of solution = volume of water + methanol

volume of solution = 80mL + 230mL = 310mL

Determine the required percent v/v

Hence the percent volume/volume of a solution that contains 80 ml of methanol and 230 ml of water is 25.81%

Chemical reactions are reversible, which means that the reaction that occurs from the reactants to form products can be also from the products to form the reactants again, this is widely studied in Chemical Equilibrium and Le Chantelier's principleons are

In an effort to stretch already thin educational budgets, a county’s school cut home economics from their offered programs fast forward to 10 years down the road then the county has a higher rate of college graduates and the median income has risen

Home economics be thought in the school again because student all over the world can be empowered by home economics programs by learning essential life skills that, occasionally, cannot be gained from textbooks or parents

And most significantly the knowledge and ability acquire on the home economic class give every student the confidence and positive reinforcement they require

Due to fact that it cover important concepts related to the family house, clothes, and food, this subject aids society in advancing human growth

Human advancement is essential to the development of society and also building essential life skills

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The statement in its interaction with hemoglobin, oxygen is a prosthetic group is False (Option 4).

The hemoglobin protein of the red blood cells is a protein that binds to oxygen in order to transport this reactant of cellular respiration to all cells of the body.

Therefore, with this data, we can see that the hemoglobin protein of the red blood cells is required to bind oxygen which does not act as a prosthetic group and is a reactant of cellular respiration.

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Answer:

Explanation:

When an electron moves from one energy level to another, energy is either absorbed or released

When an electron moves from a lower to a higher energy level, energy is absorbed. When an electron moves from a higher level to a lower level, energy is released

Since the electron moves from a lower level 3 to a higher level 5, emergy is absorbed

Thus, movement from 3 to 5 is the answer

Bromination of isobutane is a two‑step reaction.

The enthalpy of each step : step 1: ΔH = 34 kJ/mol. step 2 : ΔH = -99 kJ/mol  enthalpy of the overall reaction , ΔH = 65 kJ/mol.

Bond dissociation energy :

H - H = 436 kJ/mol

H - Br = 366 kJ/mol

Br - Br = 193 kJ/mol

(CH₃)₃C - H = 400 kJ/mol

(CH₃)₃C - Br = 292 kJ/mol

Step 1 : (CH₃)₃C - H   +   Br    ------>   (CH₃)₃C°    +   H - Br

ΔH = ∑ Bond broken - ∑ Bond form

ΔH = 400 kJ/mol - 366 kJ/mol

ΔH = 34 kJ/mol    

Step 2: (CH₃)₃C°   +  Br - Br ---->    (CH₃)₃ - Br    +  Br

ΔH = ∑ Bond broken - ∑ Bond form

ΔH = 193 - 292

ΔH = - 99 kJ/mol

overall reaction :

(CH₃)₃ - H  +  Br - Br ---->    (CH₃)₃ - Br   +   H- Br

ΔH = ( 400 + 193 ) - ( 292 + 366 )

ΔH = 593 - 658

ΔH = - 65 kJ/mol

Thus, Bromination of isobutane is a two‑step reaction.

The enthalpy of each step : step 1: ΔH = 34 kJ/mol. step 2 : ΔH = -99 kJ/mol  enthalpy of the overall reaction , ΔH = 65 kJ/mol.

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Answer:862470.84

Explanation:

1 mole of substance is exactly equal to 6.023 × 10 ²³ molecules. 843.22 × 10²³ atoms are in 140 moles of Gold.

The term mole is defined as the amount of substance of a system which contains as many elementary entities.

1 mole is equal to 6.023 × 10 ²³ molecules.

One mole of any substance is equal to 6.023 × 10²³ units of that substance such as atoms, molecules, or ions. The number 6.023 × 10²³ is called as Avogadro's number or Avogadro's constant.

The mole concept can be used to convert between mass and number of particles.

1 mole = 6.023 × 10²³ molecules ( Avogadro number )

Then 1 mole of gold = 6.023 × 10²³ molecules

140 moles of gold = 140 × 6.023 × 10²³

=  843.22 × 10²³ atoms

Thus, 843.22 × 10²³ atoms are in 140 moles of Gold.

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The term that describes how difficult it is to remove a valence electron from an atom of a particular element is electron affinity (option A).

Electron affinity is the energy released when an electron is attached to an atom or molecule; used as a measure of its ability to form an anion.

It becomes harder to remove an electron when an atom has a net positive charge because the attraction that the nuclear charge exerts per electron gets larger.

It takes a large amount of energy to remove electrons from an element with high electron affinity, hence, electron affinity determines how difficult it is to remove a valence electron from an atom.

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In this question, we have to find which ions are classified as spectator ions. The definition of spectator ions is the ones that will not participate directly in any change in the reaction.

In a reaction we usually have 2 main changes for the ions, they can change their oxidation number, in a reaction called redox reaction. They can also change their physical state, going from aqueous to solid.

The spectator ions will not have their oxidation number changed and they will not change their physical state.

The 2 ions that can be classified as spectator ions are Na+ and NO3-

Answer: son Na+ y NO3-

Explanation:

Answer:

B. Less than 1.7.

Explanation:

A covalent bond can be polar o non polar, but if the electronegativity difference between the atoms is less than 1.7 will be covalent polar and it will be covalent nonpolar if it is less that 0.5.

Answer

Reduction

Procedure

A redox reaction is a reaction that involves the transfer of electrons between chemical species. During a redox reaction, some species undergo oxidation, or the loss of electrons, while others undergo reduction or the gain of electrons.

An atom’s oxidation number is the charge that the atom would have if all of the bonds to the atom were completely ionic. An increase in oxidation number during a reaction corresponds to oxidation, while a decrease corresponds to reduction.

In a synthesis reaction, two or more reagents react to form a new product. In decomposition reactions, a single reagent is separated into two or more new products.

According to the given equations:

Phosphorus and hydrogen react to form a new product which is phosphane.

It means that the first is a synthesis reaction.

Hydrogen and oxygen react to form a new product which is water.

It means that the second is also a synthesis reaction.

The battery works by using electrochemical processes known as oxidation and reduction. Electrons are exchanged between chemical entities in these reactions. Oxidation occurs when a chemical species loses one or more electrons. The opposing process, electron gain, is known as reduction.

An oxidation process occurs at the positive electrode during discharge, whereas a reduction reaction occurs at the negative electrode. Electrons from an external power source induce a reverse electrochemical reaction in the rechargeable battery.

Calcium does not readily oxidize in dry air at normal temperatures, but it oxidizes fast in wet air or dry oxygen at around 300°C. Calcium interacts with fluorine at ambient temperature and with the other halogens at 400°C. Calcium is a great reducing agent and is extensively employed for this purpose.

Note that the question seems incomplete hence the general answer.

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In this question, we need to calculate the percent mass concentration of one solute in one solvent, and we have:

178mg of C6H12O6

4.91g of H2O

To calculate the mass percent concentration, we can use the following formula:

%mass = (mass of solute/mass of solution)*100

But first, we need to have both compounds in the same unit, so 178mg will be equal to 0.178g

Now we add these values into the formula:

%mass = (0.178/5.088) * 100

mass = 3.50%

The 5.088 is because 4.91 + 0.178

The mass of Iron produced by the reaction of given reactants will be 64.3 grams.

The balanced reaction is given as,

Fe₂O₃ + 3CO= 2Fe + 3CO₂

According to the chemical equation, 3 moles of carbon monoxide, CO, will react with 1mole of ferric oxide, Fe₂O₃, and produce 3 moles of carbon dioxide, CO₂

Now, we are given moles of carbon monoxide and asked for moles of Iron. This means that we will have to convert the aforementioned mole ratio that exists between carbon monoxide and carbon dioxide to a gram ratio.

If one mole of Iron has the mass of 55.845 g and one mole of carbon dioxide has a mass of 44.01 g, it follows that  reaction produces

44.01g of carbon dioxide for the every 55.845 g of Iron.

So for 1 moles of carbon dioxide the mass will be  44.01 g

For 3 moles it is 3× 44.01 =132.03 gram

1 mole carbon dioxide has 55.845 g iron

0.576 moles has 55.845×0.576

44.01×3 g of carbon dioxide = 132.03 g

55.845×2 g of Iron = 111.69 g

So in 0.576 moles it will get 111.69×0.576

=64.3 grams of Iron are produced.

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The rate of the reaction usually depends on the concentration of the reactants. We have to reactants in this reaction, sulfuric acid and sodium thiosulfate. Let's look at the values that were recorded.

The volume of sulfuric acid that is added is constant, but the volume of sodium thiosulfate is not. It decreases and the volume of water increases, so we are diluting the sodium thiosulfate. The concentration of one reactant is decreasing. So the rate of the reaction is also decreasing. Then the time that it takes for the cross to become invisible should increase.

Answer: the time should increase.

Explanation:

The degree of amines is determined by the number of carbons attached to the nitrogen.

According to the given picture, the answer is A.

Answer:

The answer is A.

So,

Let's first convert some units:

So,

There's a reaction between 12.9g of sodium chloride and 250g of silver nitrate.

The reaction that occurs here, is the next one:

Sodium chloride reacts with silver nitrate to form silver chloride and sodium nitrate.

This reaction is a displacement reaction.

Now, let's complete the information:

Formula of Reactant A: NaCl

Grams of Reactant A: 12.9g

Formula of Reactant B: AgNO3

Grams of Reactant B: 250g

Formula of Product C: AgCl

Grams of Product C: ?

Formula of Product D: NaNO3

Grams of Product D: ?

We need to find the amount of grams of the formed products.

So, let's first convert the grams of each reactant in moles. Remember that the number of moles (n) can be found if we divide the given mass of the given compound by its molar mass. So,

The limiting reactant in this reaction is NaCl. So, we're going to use the reaction's stoichiometry to find the amount of the products as follows:

Thus, there are 31.53g of AgCl formed.

Finally, let's find the amount of grams of product D (NaNO3):

Therefore,

There were formed 31.53g of AgCl (product C) and 18.69g of NaNO3 (product D)