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Which layer of the atmosphere reflects radio waves back to Earth?
A. Mesosphere
B. Stratosphere
C. Thermosphere
D. Troposphere

The mass of ammonium chloride that must be added is : ( A ) 4.7 g

Given data :

Volume of water ( V )  = 250 mL = 0.25 L

pH of solution = 4.85

Kb = 1.8 * 10⁻⁵

Kw = 10⁻¹⁴

Given that the dissolution of NH₄Cl gives NH₄⁺⁺ and Cl⁻ ions the equation is written as :

NH₄CI  +  H₂O  ⇄  NH₃ + H₃O⁺

where conc of H₃O⁺

[ H₃O⁺ ] = [tex]\sqrt{Ka.C}[/tex]   and Ka = Kw / Kb

∴ Ka = 5.56 * 10⁻¹⁰

Next step : Determine the concentration of H₃O⁺  in the solution

pH = - log [ H₃O⁺ ] = 4.85

∴ [ H₃O⁺ ] in the solution = 1.14125 * 10⁻⁵

Next step : Determine the concentration of NH₄CI in the solution

C = [ H₃O⁺ ]² / Ka

  = ( 1.14125 * 10⁻⁵ )² /  5.56 * 10⁻¹⁰

  = 0.359 mol / L

Determine the number of moles of NH₄CI in the solution

n = C . V

  = 0.359 mol / L  * 0.25 L =  0.08979 mole

Final step : determine the mass of ammonium chloride that must be added to 250 mL

mass = n * molar mass

         = 0.08979 * 53.5 g/mol

         = 4.80 g  ≈ 4.7 grams

Therefore we can conclude that the mass of ammonium chloride that must be added is 4.7 g

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Answer:

The answer is C

Explanation:

Just took the test

Hydrogen bonding is the intermolecular interaction that occurs due to electronegativity differences. Substance B has stronger bonds and requires more energy. Thus, option B is correct.

Hydrogen bonding is present in the water molecules that is because of the electronegativity differences and the dipole-dipole interaction. The hydrogen of the water molecule is bonded to the oxygen molecule.

The hydrogen bonding affects the boiling and the melting point of the substances as more energy are required to change the phase of the matter. So when substance B requires 100ºC than substance A (78.4ºC) it shows strong hydrogen bonding.

Therefore, option B. substance B has a strong hydrogen bond is correct.

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The volume of water needed to make the solution is 473.76 mL

We'll begin by calculating the volume of the diluted solution.

M₁V₁ = M₂V₂

15.5 × 5.41 = 0.175 × V₂

83.855 = 0.175 × V₂

Divide both side by 0.175

V₂ = 83.855 / 0.175

V₂ = 479.17 mL

Finally, we shall determine the volume of water needed.

Volume of water = V₂ – V₁

Volume of water = 479.17 – 5.41

Volume of water = 473.76 mL

Therefore, the volume of the water needed is 473.76 mL

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Answer:

False

Explanation:

As I like to think of it, equilibrium will shift either 'forwards' (to increase products) or 'backwards' (to increase reactants) to oppose any change in system;

If heat is added, the equilibrium will shift in the direction that reduces heat within the system;

In other words, it will shift in favour of the endothermic reaction, i.e. the reaction where heat is gained by the molecules/atoms and therefore taken out from the system;

If the 'forwards' reaction, producing NH₃, is exothermic (i.e. energy is released in the reaction), then the 'backwards' reaction is endothermic;

So the equilibrium will shift in this direction, which is the reaction of 2 NH₃ molecules producing N₂ and 3 H₂

The acid ionization constant is the quantitative measure of the acidic strength. For oxalic acid, Ka = [H⁺] [HC₂O₄⁻] / [H₂C₂O₄]

Acid dissociation (Ka) is the ratio of the concentration of the conjugate base and hydrogen ion to the concentration of the chemical.

Oxalic acid is a weak acid and gets dissociated as:

H₂C₂O₄ ⇌ H⁺ + HC₂O₄⁻

or

HC₂O₄⁻ ⇌ H⁺ + C₂O₄²⁻

The acid ionization constant for the reactant and the product is given as:

Ka = [H⁺] [A⁻] / [HA]

Ka = [H⁺] [HC₂O₄⁻] / [H₂C₂O₄]

Therefore, the ionization constant for oxalic acid is given as Ka = [H⁺] [HC₂O₄⁻] / [H₂C₂O₄]

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This question is describing two chemical equations whereby the concentration of ammonia has to be determined. The first reaction is between 25.00 mL of ammonia and 50.00 mL of 0.100-M HCl whose excess was neutralized with 21.50 mL of 0.050-M Na₂CO₃ and thus, the concentration ammonia in the cloudy solution was determined as 0.114 M.

First of all we need to go over the titration of the excess HCl with Na₂CO₃ by writing the chemical equation it takes place when they react:

[tex]2HCl+Na_2CO_3\rightarrow 2NaCl+CO_2+H_2O[/tex]

Whereas the mole ratio of HCl to Na₂CO₃ is 2:1 and the volume of the HCl leftover is determined as follows:

[tex]V_{HCl}^{leftover}=\frac{2*0.050M*21.50mL}{0.100M} =21.5mL[/tex]

Next, we infer that the consumed volume of HCl by the ammonia solution was:

[tex]V_{HCl}^{consumed}=50.00mL-21.50mL=28.5 mL[/tex]

Then, we write the chemical equation that takes place between ammonia and HCl:

[tex]HCl+NH_3\rightarrow NH_4Cl[/tex]

Whereas the mole ratio is now 1:1, which means that the concentration of ammonia was:

[tex]M_{NH_3}=\frac{28.5mL*0.100M}{25.00mL}\\\\ M_{NH_3}=0.114M[/tex]

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Explanation:

it is a parallel circuit.

hope this helps you.

boron, carbon, nitrogen, oxygen and flourine families in addition to the noble gases.

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also to answer the 'hello guys what is good!':nothin u?

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According to Dalton's atomic theory, atoms of different elements combine in simple whole-number ratios to form compounds.

As the name implies, Dalton's atomic theory is a theory proposed by an English scientist named John Dalton in the 1900's.

The Dalton's atomic theory is composed of five main parts, which are as follows:

Therefore, in accordance to Dalton's atomic theory, atoms of different elements combine in simple whole-number ratios to form compounds.

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Answer:

So, Percentage Composition of Aluminium = 2778×100%=34.62% (approx.) Percentage Composition of Oxygen = 3×1678×100%=61.54% (approx.)

Answer:

2. 389.15K , 3. 229.15K

Explanation:

K-273.15 = °C

Taking into account the reaction stoichiometry and limiting reagent, 0.7977 grams of KClO₃ are formed from the  reaction of 2.50 g of KClO₄  with 150 mg of FeCl₂  in excess of H₂SO₄.

In first place, the balanced reaction is:

2 FeCl₂ + 13 KClO₄ + H₂SO₄ → 2 Fe(ClO₃)₃ + K₂SO₄ + 11 KClO₃ + H₂O

By reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of moles of each compound participate in the reaction:

The molar mass of the compounds is:

Then, by reaction stoichiometry, the following mass quantities of each compound participate in the reaction:  

The limiting reagent is one that is consumed first in its entirety, determining the amount of product in the reaction. When the limiting reagent is finished, the chemical reaction will stop.

To determine the limiting reagent, it is possible to use the reaction stoichiometry of the reaction and a simple rule of three as follows: if by stoichiometry 1801.15 grams of KClO₄ reacts with 253.5 grams of FeCl₂, if 2.50 grams of KClO₄ react how many mass of FeCl₂ will be needed?

[tex]mass of FeCl_{2}=\frac{2.50 grams of KClO_{4} x253.5 grams of FeCl_{2}}{1801.15 grams grams of KClO_{4}}[/tex]

mass of FeCl₂=0.35 grams

But 0.35 grams of FeCl₂ are not available, 150 mg= 0.150 grams (being 1000 mg= 1 grams) are available. Since you have less mass than you need to react with 1801.15 grams of KClO₄, FeCl₂ will be the limiting reagent.

Then the following rule of three can be applied: if by reaction stoichiometry 253.5 grams of  FeCl₂ form 1348.05 grams of KClO₃, 0.150 grams of FeCl₂ form how much mass of KClO₃?

[tex]mass of KClO_{3}=\frac{0.150 grams of FeCl_{2}x1348.05 grams of KClO_{3} }{253.5grams of FeCl_{2} }[/tex]

mass of KClO₃= 0.7977 grams

Then, 0.7977 grams of KClO₃ are formed from the  reaction of 2.50 g of KClO₄  with 150 mg of FeCl₂  in excess of H₂SO₄.  

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1. The neutral atoms of lead has 82 protons.

2. The ions of lead also have 82 protons.

The correct answer to the question is Option D. Neutral atoms of lead must have 82 protons. Ions must have 82 protons, as well.

Lead, Pb is a metal with an atomic number (i.e proton number) of 82

Metals can only form ions by losing their valence electron(s)

NOTE: In the formation of ions, only the electrons are involved. The protons are not involved. Thus, the protons of the neutral atom and the ion remains the same.

With the above information in mind, we can conclude that neutral atoms of lead must have 82 protons. Ions must have 82 protons, as well.

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Answer:

C. Neutral atoms of lead must have 82 neutrons, but ions can have more or fewer

Explanation:

O Neutral atoms of lead must have 82 neutrons, but ions can have more or fewer. O Neutral atoms of lead must have 82 protons, but ions can have more or fewer.

Answer:

A.

The answer is A :)

Answer:

b

Explanation:

OH and CN both have -1 charges

I hope it help u =)

Brainliest answer pls

Answer: Trees, like all plants, are alive and require nutrients to survive. ... This dormancy is what allows trees to survive the cold winter. During dormancy, a tree's metabolism, energy consumption, and growth all slow down significantly in order to endure the harsh season of winter when water and sunlight are more scarce

Explanation: mark me brainlest plz if this helped only !

Answer:

False

Explanation:

Fluid pressure has no direction, being a scalar quantity, whereas the forces due to pressure have well-defined directions: They are always exerted perpendicular to any surface. The reason is that fluids cannot withstand or exert shearing forces.

mol = conc × v

= 1.5 × 0.09

= 0.135 moles of HCl

HCl + NaOH > NaCl + H2O

1 mole HCl = 1 mole NaOH

0.135 mol HCl = x

x = 0.135 mol NaOH

mass = mol × molar mass

= 0.135 × 40

= 5.4 g

NaOH = 23 + 16 + 1 = 40 g/mol

I'm not a 100% sure if it's correct

There are 6.44 × 10²³ molecules in 24.0 L of oxygen gas at standard temperature and pressure.

HOW TO CALCULATE NUMBER OF MOLECULES:

To calculate the number of molecules in a substance, we need the number of moles. The number of moles can be calculated using ideal gas law equation as follows:

PV = nRT

Where;

According to this question, oxygen gas is at standard temperature (273K) and pressure (1 atm)

1 × 24 = n × 0.0821 × 273

24 = 22.4n

n = 24 ÷ 22.4

n = 1.07moles

To calculate the number of molecules, we multiply the no. of moles by Avogadro's number (6.02 × 10²³)

no. of molecules = 1.07 × 6.02 × 10²³

no. of molecules = 6.44 × 10²³

Therefore, there are 6.44 × 10²³ molecules in 24.0 L of oxygen gas at standard temperature and pressure.

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Explanation:

brain and heart froce acts between two chloramine

Answer:

Dispersion, Hydrogen-bonding, and Dipole forces act between two chloramine (NH2CI) molecules.

Explanation:

Dispersion is exerted between all molecules. Chloramine is polar, therefore dipole forces are present. The molecular geometry of chloramine (NH2Cl) is a trigonal pyramidal, therefore hydrogen-bonding forces are present.

Answer:

The egg will gain mass.

Explanation:

Eggs soaked in distilled water will gain mass and appear dramatically swollen.

Answer:

Gain mass

Explanation:

Carbonated water will create a reaction inside the egg making the fluid inside the egg becoming more solid thus gaining mass

Hope this helps!

Answer:

absorption or precipitation or by both

Explanation:

Answer:

D. The bike experiences a contact force and Earth experiences a non-contact force.

Answer:D. The bike experiences a contact force and Earth experiences a non-contact force.

Explanation:

why is because tthe force wil make the bikw wobbly and boom no contact force

Answer:

Explanation:

Gravity pulls the balls down the ramp, and the force of gravity is bigger on larger-mass objects. The extra force on the bigger ball means that it has more energy when it gets to the bottom of the ramp and consequently travels more before stopping.

Science can be defined as the study of nature, its behaviors and the

interactions between the various components.

Science is divided into three main branches which are

Science can also be referred to as the gaining of knowledge through various

methods and verifiable by experiments to ensure it is valid.

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Answer:

Potassium is more reactive than aluminium, so no reaction takes place. But aluminium is more reactive than copper, so it replaces the copper in copper nitrate

More reactive metal compound + less reactive metal

-> no reaction

However

Less reactive metal compound + more reactive metal

-> more reactive metal compound + less reactive metal

This is called substitution reaction where the more reactive metal replaces the less reactive metal in the compound.

The replacement reaction will not occur because iodine is less reactive than chlorine.

A replacement reaction is a type of reaction in which one element is replaced by another in a compound.

The principle behind one element replacing the other is based on the reactivity of an element. A more reactive element will displace a less reactive one.

According to this question, the following displacement reaction is given: MgCl2 + I2 → ?

This reaction will not occur because chlorine is more reactive/electronegative than iodine, hence, iodine cannot displace it.

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