Help in history class please Thnks

Answer:

3.43×10¹ mol

Explanation:

Given data:

Initial number of  moles = 12.4 mol

Initial volume = 122.8 L

Final volume = 339.2 L

Final number of moles = ?

Solution:

The number of moles and volume are directly proportional to each other at same temperature and pressure.

Formula:

V₁/n₁  =  V₂/n₂

Now we will put the values,

122.8 L/ 12.4 mol  =  339.2 L / n₂

n₂ = 339.2 L× 12.4 mol  / 122.8 L

n₂ = 4206.08 L.mol /122.8 L

n₂ = 34.3mol

In scientific notation:

3.43×10¹ mol

Answer:

0.52g of Al(OH)₃

Explanation:

The reaction of aluminium nitrate, Al(NO₃)₃, reacts with KOH, as follows:

Al(NO₃)₃ + 3KOH → Al(OH)₃ + 3 KNO₃

That means 1 mole of aluminium nitrate reacts with 3 moles of potassium hydroxide.

To find moles of aluminium hydroxide we need to determine the limiting reactant finding moles of each reactant:

Moles aluminium nitrate:

0.050L * (0.20mol / L) = 0.01 moles Al(NO₃)₃

Moles KOH:

0.200L * (0.100mol / L) = 0.02 moles of KOH

Thus, for a complete reaction of 0.02 moles of KOH are needed (Using the chemical equation)

0.02 moles of KOH * (1 mol Al(NO₃)₃ / 3 mol KOH) = 0.0067 moles of Al(NO₃)₃.

As there are 0.01 moles of Al(NO₃)₃, this is the excess reactant and KOH is the limiting reactant.

The 0.02 moles of KOH produce:

0.02 moles of KOH * (1 mol Al(OH)₃ / 3 mol KOH) = 0.0067 moles of Al(OH)₃

In mass (Using molar mass of Al(OH)₃: 78g/mol):

0.0067 moles of Al(OH)₃ * (78g/mol) =

Answer:

cells are a basic unit of structure and function all things

Answer:

ABC

Explanation:

hrdjyt

How do the products of chemical reactions compare to their reactants?

Answer:

The products often have completely different properties than the reactants.

The correct answer to the question is: The products often have completely different properties than the reactants.

In a chemical reaction, the reactants and products of the reaction have different properties because during the reaction, bonds were broken and new bonds were formed which generate a new substance called the product.

However, chemical equations must be balanced in order to conform to the law of conservation of matter which states that matter can neither be created nor destroyed  during a chemical reaction but can be transferred from one form to the other.    

For example, the reaction of Hydrogen gas (H₂) and oxygen gas (O₂) to produce water (H₂O)

From the equation, we can see that the reactants are gases but the product is a liquid which has a different properties from the gaseous reactants.

Therefore, the correct answer to the question is:  The products often have completely different properties than the reactants.

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Answer:

wait

Explanation:

a. The pH of this solution is 9.45.

b. If 0.88 g of NaOH is added to the solution, the pH will be  9.74.

a way to gauge how basic or acidic a material or solution is. On a scale of 0 to 14, pH is measured. A pH of 7 indicates neutrality on this scale, which implies it is neither acidic nor basic. More basic substances have a pH value more than 7, whereas more acidic substances have a pH value less than 7.

first of all we should calculate the molarity of the compounds

no. of moles of NH₃ = weight / molecular weight = 1.68 / (14+3) = 0.099

no. of moles of (NH₄)2SO4 = 4.05 / {2×(14+4) + 32 + 64} = 0.031

no. of moles of NH4+ = 2×0.031 = 0.062

[NH₃] = no. of moles / volume(L) = 0.099/ 0.5 = 0.198

[(NH₄⁺] = 0.031/0.5 = 0.124

1) now we know that

pH + pOH = pkw

pOH = pkw - pH = 14 - pH ---- -1

also

pOH = pkb + log ( [salt]/[base])

from 1

14 - pH = pkb + log ( [salt]/[base])

putting values

14- pH = -log(1.8e-5) + log(0.124/0.198)

14 - pH = 4.54

pH = 9.45

2) if 0.88g NaOH is added then as we know that NaOH is a base then it will reduce the buffer capacity

as there would be OH- ions initially present

hence the buffer action will move backward

i.e

pOH = pkb + log {(salt-x) / (base+x)}

where x= molarity of NaOH

no of moles of NaOH = 0.88 / (23+16+1) = 0.022

molarity of NaOH = 0.022/0.5 = 0.044

then 14 - pH = -log(1.8e-5) + log{ (0.124-0.044) / (0.198+0.044) }

14 - pH = 4.26

pH = 9.74

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The sentence that has an accurate punctuation is found in (Option B).

The punctuation marks are those marks that are use to make a piece of writing to have a complete meaning. A piece of writing will be meaningless if there are no attached punctuation marks.

The sentence that is correctly punctuated is;  "I bought all the ingredients for dinner: eggs, tomatoes, macaroni, and cheese—and told Molly to preheat the oven."(Option B)

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Answer:  the cake rises as gas bubbles form in the cake

Explanation: Had a quizziz quiz on this

Answer: The cake rises as gas bubbles form in the baking cake.

Explanation: had a test, got it right.

Answer:

273.9m/s

Explanation:

Given parameter:

Kinetic energy of the ball  = 4.5kJ

Mass of the ball  = 120g

Unknown:

Speed of the ball  = ?

Solution:

Kinetic energy of a body is the energy due to the motion of a body.

 K.E  = [tex]\frac{1}{2}[/tex] m v²

where m is the mass

           v is the speed

Convert the quantities to the appropriate units;

     4.5kJ to J  = 4.5 x 10³J

 120g to kg  = 0.12kg

Now insert the parameters and find the unknown:

       4500  = [tex]\frac{1}{2}[/tex] x 0.12 x V²  

      9000 = 0.12V²  

       V²  = [tex]\frac{9000}{0.12}[/tex]   = 75000

        V  = 273.9m/s

Molarity after dilution : 0.0058 M

The number of moles before and after dilution is the same  

The dilution formula

 M₁V₁=M₂V₂

M₁ = Molarity of the solution before dilution  

V₁ = volume of the solution before dilution  

M₂ = Molarity of the solution after dilution  

V₂ = Molarity volume of the solution after dilution

M₁=0.1 M

V₁=6.11

V₂=105.12

[tex]\tt M_2=\dfrac{M_1.V_1}{V_2}=\dfrac{0.1\times 6.11}{105.12}=0.0058~M[/tex]

Answer:

6,500 gm of steam require= 3,510 kilo calories (approx)

Explanation:

Every 1 gram of water at 100° C  absorb 540 calories

So,

Total water = 6.5 kg = 6,500 gram

So,

6,500 gm of steam require = 6,500 x 540

6,500 gm of steam require= 3,510 kilo calories (approx)

According to the question,

Total water,

Temperature,

Now,

Required steam will be:

= [tex]6500\times 540[/tex]

= [tex]3510 \ kilo \ calories[/tex]

Thus the above answer is right.

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Answer:

(a) > (d) > (c) > (b)

Explanation:

Acidic character is based upon inductive effect of the functional group that are attached to parent chain.

1. Nitro is a -I group which makes phenol acidic due to increased resonance,  2. bromine is a -I group but it is weaker than nitro group

3. phenol is more acidic than cyclohexanol due to resonance stabilization of resonance and among halogen F>Cl>Br>I is the order of acidity

4. cyclohexanol will be weakest as  it is not associated with any -I groups here.

so the order of acidity will be

(a). 4-nitropheno >  (d). 4-bromophenol > (c). 2,6-difluorocyclohexanol  >               (b). cyclohexanol

Answer:

its B

Explanation:

Because its can only go cold to hot. -hope this help :)

Answer:

• All groups (columns) have the same number of valence electrons

Explanation:

Every group or column have the same number of valence electrons as a suprise. Every column is aligned in this way.

Answer:

all members within any group

Explanation:

Answer:

1.86 M

Explanation:

From the question given above, the following data were obtained:

Mass of sucrose (C12H22O11) = 22.5 g

Volume of solution = 35.5 mL

Molarity of solution =?

Next, we shall determine the number of mole in 22.5 g of sucrose (C12H22O11). This can be obtained as follow:

Mass of sucrose (C12H22O11) = 22.5 g

Molar mass of C12H22O11 = (12×12) + (22×1) + (16×11)

= 144 + 22 + 176

= 342 g/mol

Mole of C12H22O11 =?

Mole = mass /Molar mass

Mole of C12H22O11 = 22.5 /342

Mole of sucrose (C12H22O11) = 0.066 mole

Next, we shall convert 35.5 mL to litres (L). This can be obtained as follow:

1000 mL = 1 L

Therefore,

35.5 mL = 35.5 mL × 1 L / 1000 mL

35.5 mL = 0.0355 L

Thus, 35.5 mL is equivalent to 0.0355 L.

Finally, we shall determine the molarity of the solution as follow:

Mole of sucrose (C12H22O11) = 0.066 mole

Volume of solution = 0.0355 L.

Molarity of solution =?

Molarity = mole /Volume

Molarity of solution = 0.066/0.0355

Molarity of solution = 1.86 M

Therefore, the molarity of the solution is 1.86 M.

Answer:

B

Explanation:

i just read it na, but i forgot the explanation

Answer:

A. and B.

Explanation:

Anion is negative as well as a negative ion.

(Just took the quiz)

Answer:

Hydrogen peroxide is a highly reactive chemical containing the elements hydrogen and oxygen. Pure hydrogen peroxide is a colourless liquid, but it is sold on the market as solutions in water, containing up to 33 – 37% pure hydrogen peroxide and other additives to stop the product decomposing.

Explanation:

Hope this helps <3

Answer: .063

Explanation:

1.53g Mg * (1 mol Mg/ 24.3 g Mg) * (1 mol H2/1 mol Mg) = .063 mol H2

The mole of hydrogen gas that will be produced from the reaction would be 0.0630 moles.

From the equation of the reaction:

[tex]Mg(s) + 2 HCl(aq) ---> MgCl_2(aq) + H_2(g)[/tex]

The mole ratio of Mg to H2 gas is 1:1. Thus, for every one mole of Mg consumed by the reaction, 1 mole of H2 is produced, all other things being equal.

Recall that: mole = mass/molar mass

1.53 g of magnesium = 1.53/24.3

                                     = 0.0630 mole (to 3 significant figures)

Since the mole ratio of Mg to H2 is 1:1, it means that the number of moles of hydrogen gas produced would also be 0.0630 moles.

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Answer:

[tex]E=9.62\times 10^{-21}\ J[/tex]

Explanation:

Given that,

The wavelength of a microwave is 7.42 mm or 0.00742 m

No. of photons, n = 359

We need to find the energy produced by this no of photons. It can be given by the formula as follows :

[tex]E=\dfrac{nhc}{\lambda}\\\\E=\dfrac{359\times 6.63\times 10^{-34}\times 3\times 10^8}{0.00742}\\\\=9.62\times 10^{-21}\ J[/tex]

or

[tex]E=9.62e^{-21}\ J[/tex]

So, the required energy is [tex]9.62\times 10^{-21}\ J[/tex].

Answer:

⬆️That guy deserves brainliest

Explanation:

A buffer solution is often referred to as a mixture of an aqueous solution of a weak acid and its conjugate base or weak base and its conjugate acid.

Conclusively we can say that an acid or base needed for making buffer solutions and not base alone

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Answer:

This question appears incomplete

Explanation:

There is no such element known as "Ballardium (Bu)" in the periodic table. However, there are elements with a bit of similarity in spellings and pronunciation such as Beryllium (Be) which is found in group 2 (meaning it is an alkali earth metal), Berkelium (Bk) which is an actinide (meaning it is radioactive) and Vanadium (V) which is found in group 5 of the periodic table (meaning it's a transition metal).

Answer:

D. AgN.

Explanation:

Hello!

In this case, since the boiling point of a solution increases are more solute remains dissolved in the liquid, as more energy is required to start the phase transition, for insoluble solids for which we know the solubility product which has the following relationship with the amount of ions in solution:

"the greater Ksp, the more ions the solution has"

In such a way, for the solid with the greatest Ksp we understand it has most of the ions in solution and therefore the highest boiling point, thus, among the choices, D. AgN is the one with the highest boiling point because it Ksp is 7.2E-11, whcih is the greatest.

Best regards!

Explanation:

All period have the same number of shells

Answer:

if it ain't changing direction the acceleration isn't being affected

Answer:

[tex]k=8.63x10^{-8}\frac{1}{M*s}[/tex]

Explanation:

Hello!

In this case, since the differential rate law of a second-order reaction is:

[tex]\frac{dC_A}{dt}=-kC_A^2[/tex]

Whereas A stands for NOCl and the corresponding integrated rate law is:

[tex]\frac{1}{C_A} =kt+\frac{1}{C_A_0}[/tex]

Thus, since we know the concentrations and the elapsed time, we compute the rate constant as shown below:

[tex]k=( \frac{1}{C_A}-\frac{1}{C_A_0} )/t\\\\k=( \frac{1}{0.83M}-\frac{1}{0.878M} )/763,200s\\\\k=8.63x10^{-8}\frac{1}{M*s}[/tex]

Best regards!

Answer:

The main function of the immune system is to provide immunity to the body. Immunity is the body's ability to protect itself from the pathogens it is exposed to. Immunity depends on the body's ability to differentiate between things that belong in the body and those that do not. The immune system's first line of defense includes physical and chemical barriers that are always ready and prepared to defend the body from infection.

The skin acts as a barrier against pathogens. Some structures of the first line of defense include the skin, mouth, eyes, ears, nose, and stomach. The skin produces sweat and oil that work together to keep pathogens from the entering the body. Saliva and tears contain substances the can destroy pathogens. The ears and the stomach help fight pathogens.The ears produce ear wax that prevent pathogens from entering the ears. The stomach produces a liquid the kills pathogens.

Mucus is produce by the nose, lungs, throat, and stomach. Mucus traps pathogens. Mucus also prevent pathogens from getting into deep tissues. Anyway, the very first line of defense against any invasion of the human body is a set of physical barriers between the inside of the body and the outer world.

*my notes from edge2020*

Hope this helps ^-^

Answer:

(b) 2.60%

Explanation:

Partition coefficient of the organic compound in ether is:

9.5 = Concentration in ether / Concentration in water

In the first extraction, X is the amount of organic compound extracted:

9.5 = X/50mL / (1-X)/200mL

9.5 = 200X / (50-50X)

475 - 475X = 200X

475 = 675X

X = 0.7037g are extracted.

Remains = 1g - 0.7037g = 0.2963g

Second extraction:

9.5 = X/50mL / (0.2963-X)/200mL

9.5 = 200X / (14.815-50X)

140.74 - 475X = 200X

140.74 = 675X

X = 0.2085g are extracted.

Remains = 0.2963g - 0.2085g = 0.0878g

Third extraction:

9.5 = X/50mL / (0.0878g-X)/200mL

9.5 = 200X / (4.3899-50X)

41.70 - 475X = 200X

41.70 = 675X

X = 0.2085g are extracted.

Remains = 0.0878g - 0.0618g = 0.026g remains

Percentage: 0.026g / 1g * 100 =

Answer:

1. 4.93 = pKb of the weak base

2. pH = 12.61

Explanation:

1. When a weak base, B, is being titrated with HCl, the reaction occurs as follows:

B + HCl → BH⁺ + Cl⁻

That means the moles added of HCl are the moles of BH⁺ produced and moles of B are initial moles of B - Moles of HCl

Thus:

Moles B:

Initial moles:

0.0250L * (0.130mol / L) = 3.25x10⁻³ moles B

Moles HCl:

8.5x10⁻³L * (0.130mol / L) = 1.105x10⁻³ moles HCl

3.25x10⁻³ - 1.105x10⁻³ =

Moles BH⁺ = Moles HCl:

pH of the buffer made from B/BH⁺ is determined using H-H equation for weak bases:

pOH = pKb + log [BH⁺] / [B]

Where pOH is 14-pH = 14-9.36 = 4.64

pKb is pKb of the weak base, our unknown.

[BH⁺] could be taken as moles of BH⁺ =  1.105x10⁻³ moles

And [B] as moles of B = 2.145x10⁻³ moles B

Replacing:

pOH = pKb + log [BH⁺] / [B]

4.64 = pKb + log [1.105x10⁻³ moles] / [2.145x10⁻³ moles]

4.64 = pKb -0.288

2. When HCl and NaOH are in solution the reaction that occurs is:

HCl + NaOH → H₂O + NaCl

To find pH we need to determine, first, which reactant is in excess:

Moles HCl:

0.023L * (0.230mol / L) = 5.29x10⁻³ moles

Moles NaOH:

0.033L * (0.0230mol / L) = 7.59x10⁻³ moles

That means NaOH is in excess and after the reaction will remain:

7.59x10⁻³ moles - 5.29x10⁻³moles = 2.3x10⁻³ moles NaOH = Moles of OH⁻

In 23+33mL = 56mL = 0.056L:

2.3x10⁻³ moles OH⁻ / 0.056L = 0.0411M [OH-]

As pOH = -log [OH-]

pOH = 1.39

pH = 14 - pOH