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3 years ago

Type the correct answer in the box.

Chemistry

2 answers:

OlgaM077 [116]3 years ago

7 0

Explanation:

Mass number of an atom means the sum of total number of protons and neutrons present in an atom.

On the other hand, atomic number is the total number of protons present in an atom.

Therefore, mass number of phosphorous is 30 g/mol whereas atomic number of phosphorous is 15 g/mol.

Thus, the mass of 1 mole of phosphorus atoms is 30 grams.

tatiyna3 years ago

4 0

the mass of 1 mole of phosphorus atoms is approximately 30 g

hope this helps :)

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A titration of 25.0 mL of a solution of the weak base aniline, C6H5NH2, requires 25.67 mL of 0.175 M HCl to reach the equivalenc

Lorico [155]

Answer:

a. 0.180M of C₆H₅NH₂

b. 0.0887M C₆H₅NH₃⁺

c. pH = 2.83

Explanation:

a. Based in the chemical equation:

C₆H₅NH₂(aq) + HCl(aq) → C₆H₅NH₃⁺(aq) + Cl⁻(aq)

<em>1 mole of aniline reacts per mole of HCl</em>

Moles required to reach equivalence point are:

Moles HCl = 0.02567L ₓ (0.175mol / L) = 4.492x10⁻³ moles HCl = moles C₆H₅NH₂

As the original solution had a volume of 25.0mL = 0.0250L:

4.492x10⁻³ moles C₆H₅NH₂ / 0.0250L = 0.180M of C₆H₅NH₂

b. At equivalence point, moles of C₆H₅NH₃⁺ are equal to initial moles of C₆H₅NH₂, that is 4.492x10⁻³ moles

But now, volume is 25.0mL + 25.67mL = 50.67mL = 0.05067L. Thus, molar concentration of C₆H₅NH₃⁺ is:

[C₆H₅NH₃⁺] = 4.492x10⁻³ moles / 0.05067L = 0.0887M C₆H₅NH₃⁺

c. At equivalence point you have just 0.0887M C₆H₅NH₃⁺ in solution. C₆H₅NH₃⁺ has as equilibrium in water:

C₆H₅NH₃⁺(aq) + H₂O(l) → C₆H₅NH₂ + H₃O⁺

Where Ka = Kw / Kb = 1x10⁻¹⁴ / 4.0x10⁻¹⁰ =

When the system reaches equilibrium, molar concentrations are:

[C₆H₅NH₃⁺] = 0.0887M - X

[C₆H₅NH₂] = X

[H₃O⁺] = X

Replacing in Ka formula:

2.5x10⁻⁵ = [X] [X] / [0.0887M - X]

2.2175x10⁻⁶ - 2.5x10⁻⁵X = X²

0 = X² + 2.5x10⁻⁵X - 2.2175x10⁻⁶

Solving for X:

X = -0.0015 → False solution. There is no negative concentrations.

X = 0.001477 → Right solution.

As [H₃O⁺] = X, [H₃O⁺] = 0.001477

Knowing pH = -log [H₃O⁺]

pH = -log 0.001477

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3 years ago

What is the usable form of nitrogen that is found in the ground?

laila [671]

Nitrate

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3 years ago

The solid form of a substance is usually more dense than its liquid and gaseous forms. Similarly the liquid form is usually more

solniwko [45]

The solid form of a substance is usually more dense than its liquid and gaseous forms. Similarly the liquid form is usually more dense than the gaseous form. Ice floating in water is an exception that breaks the general density rule. So option “A” is the correct option in regards to the given question. In case of ice formation, actually the density of water decreases by about 9%. This is the main reason behind ice floating in water. Pure water has the maximum density at 4 degree centigrade.

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3 years ago

What is the relationship between the amount of substance ( concentration) and reaction rates?

jekas [21]

Answer:

Increasing the concentration of the reagents makes the collision between two molecules of the reagents more likely, thereby increasing the probability that the reaction will occur between these reagents.

As for the relationship between concentration and volume, density also comes into play, a higher volume, lower molarity and also lower concentration.

The pressure when increasing could generate a closer approach between the particles, therefore generating an increase in the reaction speed.

Pressure and volume are related but inversely proportional, therefore if the volume increases the pressure decreases and so on.

the reaction rate increases as the contact surface area increases. This is due to the fact that more solid particles are exposed and can be reached by reactant molecules.

A perfect reaction where the collision is promoted and the reaction speed advances is with the presence of a solvent, with an increase in pressure and a decrease in volume, with an increase in the exposure of the surface, with the presence of a catalyst, with increasing temperature and with increasing entrance

Explanation:

The reaction rate is defined as the amount of substance that is transformed into a certain reaction per unit of volume and time. For example, the oxidation of iron under atmospheric conditions is a slow reaction that can take many years but over time it is oxidized sooner or later by the oxygenation of its surface layer, but the combustion of butane in a fire is a reaction that happens in fractions of seconds, giving rise to an exothermic reaction with products such as CO2 and H2O

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Ganezh [65]

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