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3 years ago

What is the ph of a 0.20 M solution of NH4Cl? [Kb(NH3) = 1.8 x 10^-5]

Chemistry

2 answers:

Pavlova-9 [17]3 years ago

8 0

"NH4+ <----> NH3 + H+

The constant of this equilibrium is: K = Kw / Kb = 1 x 10^-14 / 1.8 x 10^-5 =5.56 x 10^-10

5.56 x 10^-10 = x^2 / 0.20-x

x = [H+] =1.1 x 10^-5 M

pH = 5.0"

ad-work [718]3 years ago

5 0

Answer:

5.0

Explanation:

NH₄Cl is a strong electrolyte that ionizes according to the following equation.

NH₄Cl(aq) → NH₄⁺(aq) + Cl⁻(aq)

NH₄⁺ is a weak acid according to the following equation.

NH₄⁺(aq) ⇄ NH₃(aq) + H⁺(aq)

Given Kb for NH₃, we can calculate the Ka for NH₄⁺.

Ka. Kb = Kw

Ka = Kw / Kb = 10⁻¹⁴/1.8 × 10⁻⁵ = 5.6 × 10⁻¹⁰

For a weak acid, we can find [H⁺] using the following expression.

[H⁺] = √(Ca × Ka) = √(0.20 × 5.6 × 10⁻¹⁰) = 1.1 × 10⁻⁵ M

where,

Ca: concentration of the acid

The pH is

pH = -log [H⁺] = -log 1.1 × 10⁻⁵ = 5.0

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Answer:

1. No, you cannot calculate the solubility of X in water at 26ºC.

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You cannot calculate the solubility of X in water at 26 degrees Celsius because you do not know whether the solution formed by dissolving the crystals in 3.00 liters of water is saturaed or not.

The only way to determine the solubility of the compound X is by dissolving the crystals in certain (measured) amount of water and making sure that some crystals remain undissolved, as a solid on the bottom of the beaker.

Next, you should filter the solution to remove the undissolved crystals. Then, weigh the solution, evaporate, wash, dry, and weigh the crystals.

Then you have the mass of the crystals dissolved and the mass of the solution which will let you calculate the mass of pure water, and then the solubility.

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3 years ago

Calculate the number of moles in 136g of ammonia

amm1812

Answer:

8moles

Explanation:

We are given the mass of ammonia to be 136g

Ammonia = NH₃

Let us find the number of moles in ammonia;

Number of moles = $\frac{mass}{molar mass}$

Molar mass of ammonia = 14 + 3(1) = 17g/mol

so;

Number of moles = $\frac{136}{17}$ = 8moles

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3 years ago

Draw and label the parts of a helium atom. Include the mass and charge of each subatomic particle.

mihalych1998 [28]

Explanation:

Helium is the second element on the periodic table.

Information about helium:

it belongs to group O on the periodic table
it is has an atomic number of 2
Helium exists naturally as gas and it is nonreactive.

To write an atom we use this format:

ₙᵇGˣ

G is the symbol of the atom

n is the atomic number

b is the mass number

x is the charge on the atom

Using the periodic table as guide

Symbol of helium is He

Atomic number of helium is 2

mass number of helium is 4

charge on helium atom is 0

⁴₂He

Every atom contains protons, neutrons and electrons;

Electrons are negatively charged. For a neutral atom, the number of electrons is the same as that of protons.

Protons are positively charge particles in an atom. The atomic number is the number of protons in an atom.

neutrons do not have charges.

Helium has:

Number of protons = 2

Number of electrons = 2

Number of neutrons = 2

Mass of each subatomic particle:

1 electron = 9.11 x 10⁻³¹kg

2 electrons = 1.82 x 10⁻³⁰kg

Protons and neutrons have the same mass:

1 proton = 1.67 x 10⁻²⁷kg

2 protons = 3.34 x 10⁻²⁷kg

2 neutrons = 3.34 x 10⁻²⁷kg

Learn more:

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3 years ago

Investigate: Note the empty jars on the shelf that can be filled by using the slider. Set the amount to 2.000 moles of carbon (m

balandron [24]

Answer:

The molar mass of carbon

Explanation:

Before the mass (in grams) of two moles of carbon can be determined, the molar mass of the element would be needed.

This is because the number of mole of an element is the ratio of its mass and the molar mass. That is,

number of mole = mass/molar mass

Hence, the mass of elements can be obtained by making it the subject of the formular;

mass = number of mole x molar mass

Therefore, the molar mass of carbon would be needed before the mass of 2 moles of the element can be determined.

3 0

2 years ago

How much heat must your body transfer to 500.0g of water to heat it from 25.0°C to body temperature, 37.0°C?

shtirl [24]

Answer : The heat your body transfer must be, 25.1 kJ

Explanation :

Formula used :

$Q=m\times c\times \Delta T$

or,

$Q=m\times c\times (T_2-T_1)$

where,

Q = heat = ?

m = mass of water = 500.0 g

c = specific heat of water = $4.18J/g^oC$

$T_1$ = initial temperature = $25.0^oC$

$T_2$ = final temperature = $37.0^oC$

Now put all the given value in the above formula, we get:

$Q=500.0g\times 4.18J/g^oC\times (37.0-25.0)K$

$Q=25080J=25.1kJ$

Therefore, the heat your body transfer must be, 25.1 kJ

3 0

3 years ago