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MrRa [10]
3 years ago
6

1. Three different observers measure the melting point of a substance and agree on the

Chemistry
1 answer:
Naddik [55]3 years ago
7 0

d. precise but not accurte

You might be interested in
What volume of carbon dioxide gas at STP is required to produce 456.9g of lithium carbonate?
Margarita [4]

Answer:

It would have to be around 9.8 volume

Explanation:

7 0
3 years ago
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 =

<em>2.5x10⁻⁵ = [C₆H₅NH₂] [H₃O⁺] / [C₆H₅NH₃⁺]</em>

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

<h3>pH = 2.83</h3>

7 0
3 years ago
Write a balanced net ionic equation to show why the solubility of Cu(OH)2(s) increases in the presence of a strong acid and calc
Helga [31]

Answer:

2.2×10^8

Explanation:

Cu(OH)2(s)<---------> Cu^2+(aq) + 2OH^-(aq) Ksp=2.2 x 10 ^-20

2H3O^+(aq) + 2OH^-(aq) <-------> 4H2O(l). Kw= 1×10^14

Cu^2+(aq) + 4H2O(l) <--------> [Cu(H2O)4]^2+(aq)

Overall ionic reaction:

Cu(OH)2(s) +2H3O^+(aq) <---------> [Cu(H20)4]^2+(aq)

Equilibrium constant for the reaction: Ksp×Kw= 2.2 x 10 ^-20 × (1/(1×10^-14))^2

Keq= 2.2×10^8

Kw= ion dissociation constant of water

3 0
2 years ago
What form of waste cannot be recycled to make new products?
skelet666 [1.2K]
~Hello there! ^_^

Your question: What form of waste cannot be recycled to make new products..?

Your answer: Food is a form of waste that cannot be recycled to make new products.

Happy Studying! =)


4 0
3 years ago
Read 2 more answers
1. The basic building block of matter are atoms. Every atom is basically a tiny sphere. Every atom is composed of 2 regions, the
V125BC [204]

1. The answer is: Electron cloud.

Atom is composed of the nucleus and the electron cloud.

Protons (positive particles) and neutrons (neutral particles) are in the nucleus of an atom and electrons (negative particles) are in the electron cloud.

Nucleus is in the centar of the atom atom and electron cloud is surrounding it.

2. The answer is: Electron(s).

The electron (symbol: e⁻) is a subatomic particle whose electric charge is negative one elementary charge.

Metallic bond increace electrical and thermal conductivity.

Substances with metallic bond conduct an electric current in liquid and solid state, because they have mobile electrons. Most metals have strong metallic bond, because strong electrostatic attractive force between valence electrons (metals usually have low ionization energy and lose electrons easy) and positively charged metal ions.

3. The answer is: Nucleus.

Atomic number (Z) is total number of protons and mass number (A) is total number of protons and neutrons in a nucleus.

Nucleus of an atom has positive charge, electrons are negative and atom has neutral net charge.

For example, alpha particle is nucleus of a helium-4 atom, which is made of two protons (p⁺) and two neutrons (n°).

4. The answer is: Proton(s).

The proton (p⁺) is subatomic particle with a positive electric charge of +1e elementary charge.

Protons and neutrons, each with masses of approximately one atomic mass unit, are called nucleons.

Protons and neutrons are hadrons composed of three valence quarks.

The electron has a mass that is approximately 1/1836 that of the proton and the neutron.

5. The answer is: Neutron(s).

Neutron (symbol: n°) is a subatomic particle with no net electric charge.

Protons and neutrons are found in nucleus of an atom (atomic nuclei).  

They are called nucleons and have masses of approximately one atomic mass unit.

Mass number (A) is sum of protons and neutrons in nucleus of an atom.

6. The answer is: Direct relationship.

For example, the Hertzsprung–Russell diagram shows the relationship between the star's absolute luminosities (the total amount of energy emitted per unit of time by a star) versus their effective temperatures (the temperature of a black body that would emit the same total amount of electromagnetic radiation).

The Hertzsprung–Russell diagram puts each star on a graph according the star's brightness against its temperature.

7. The answer is: Inverse relationship.

For example, Wavelength is the inverse of the frequency.

Wavelength is the distance over which the wave's shape repeats.

The frequency is a measure of how often sinusoidal components of the wave repeat per unit of distance.  

Higher the frequency, shorter the wavelenght.

Shorter the frequncy, longer the wavelenght.

8. The answer is: No relationship.

Correlation is any statistical association, how close two variables are to having a linear relationship with each other.

If the correlation between the two variables is zero, there is no relationship

between them. So, variables have nothing to do with each other.

9. The answer is: Experimental control.

An experimental control is used in scientific experiments to minimize the effect of variables which are not the interest of the study.

The two main variables in an experiment are the independent and dependent variable.

Dependent variable is the variable being tested and measured in a scientific experiment.

Dependent variables depend on the values of independent variables. The dependent variables represent the output or outcome whose variation is being studied.

10. The answer is: Controlled variable(s).

A control variable is an experimental element which is constant and unchanged throughout the course of the experimentation.

For example, if the volume is made the control variable, it is not allowed to change it throughout the course of the experiment.

The control variables are not of primary interest to the experimenter.

7 0
3 years ago
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