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2 years ago

Cuales son los cambios que siempre envuelven cambios en la compocision de la sustancia?

Chemistry

1 answer:

QveST [7]2 years ago

3 0

I already answered this question in Spanish language. Now I answer in English.

Answer: the chemical changes.

Explanation:

We understand by composition of a substance to the proportion (ratio or percentage) of each element (type of atoms) that makes up the same, as well as the way in which these elements are linked (chemical bonds).

A chemical change is a process, also called a chemical reaction, in which one or more substances are converted into different substances.

The resulting substances are different because their composition is different, since some chemical bonds have been broken and others have been formed, giving rise to a new structure. The chemical formula of each compound product of the chemical change will present a different combination of atoms, in ratio or structure.

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The solubility of oxygen gas in water at 40 ∘c is 1.0 mmol/l of solution. What is this concentration in units of mole fraction?

juin [17]

The formula for mole fraction is:

$mole fraction of solute = \frac{number of moles of solute}{total number of moles of solution}$ -(1)

The solubility of oxygen gas = 1.0 mmol/L (given)

1.0 mmol/L means 1.0 mmol are present in 1 L.

Converting mmol to mol:

$1.00 mmol\times \frac{1 mol}{1000 mmol} = 0.001 mol$

So, moles of oxygen = 0.001 mol

For moles of water:

1 L of water = 1000 mL of water

Since, the density of water is 1.0 g/mL.

$Density = \frac{mass}{volume}$

$Mass = 1.0 g/ml\times 1000 mL = 1000 g$

So, the mass of water is 1000 g.

Molar mass of water = 18 g/mol.

Number of moles of water = $\frac{1000 g}{18 g/mol} = 55.55 mol$

Substituting the values in formula (1):

$mole fraction = \frac{0.001}{55.55+0.001}$

$mole fraction = 1.8\times 10^{-5}$

Hence, the mole fraction is $1.8\times 10^{-5}$ .

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2 years ago

After severe dust storms in the 1930s, practices were put in place to reduce soil erosion. Which

timurjin [86]

Answer: Farmers were paid to practice soil-conserving techniques like crop rotation and terracing

Explanation:

read about it here: https://www.pbs.org/wgbh/americanexperience/features/dust-bowl-surviving-dust-bowl/

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2 years ago

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Explain what happens to temperature and energy as molecules move from gas to liquid to solid

aleksley [76]

Answer and Explanation:

As the temperature of the substances increases, the average energy of the molecules increases, and average energy of attraction between the molecules decreases consequently intermolecular spacing between the molecules increases. As a result, a substance change in succession from gas to liquid to solid.

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2 years ago

Conservation of mass was discussed in the background. Describe how conservation of mass (actual, not theoretical) could be check

Sedbober [7]

Answer:

Conservation of mass can be checked in an experiment . There are three steps to do it in a best way:

1. Weigh all the equipment and materials required in the experiment before the experiment.

2. Avoid spillage and evaporation during the experiment.

3. Weigh all the equipment and materials after the experiment.

If the mass is conserved then weight from step 1 is equal to weight from step

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2 years ago

Which of the following aqueous solutions would have the highest boiling point? 3.0 M solution of molecular compound sucrose (C12

Ne4ueva [31]

Answer: option b) 3.0 M solution of ionic compound aluminum chloride (AlCl₃)

Explanation:

1) The solutions given are:

a) 3.0 M solution of molecular compound sucrose (C₁₂H₂₂O₁₁)

b) 3.0 M solution of ionic compound aluminum chloride (AlCl₃)

c) 3.0 M solution of ionic compound lithium bromide (LiBr)

d) 3.0 M solution of ionic compound calcium fluoride (CaF₂)

2) The elevation of the boiling point of a solution is a colligative property.

3) That means that the elevation of the boiling point depends on the number of solute particles in the solvent and not the identity per se of the solute particles.

4) The formula of the elevation of the boiling point, ΔTb is:

ΔTb = i × m × Kb.

Where:

i) i is the Van't Hoof constant and is equal to the number of particles for each molecule or unit formula.

If the compound is a molecule (covalent bond) i = 1, if the compound is ionic, i is the number of ions product of the dissociation (I will show you how to determine it for each of the compounds given).

ii) m is the molality of the solution (moles of solute per kg of solvent)

iii) Kb is the molality boiling constant. It is a constant for every solvent. It does not change with the solute.

4) For our four compounds, m and kb are egual, so you must analyze the i factor for each solution.

a) 3.0 M solution of molecular compound sucrose (C₁₂H₂₂O₁₁)

Since it is a molecular compound it does not dissociate and i = 1

b) 3.0 M solution of ionic compound aluminum chloride (AlCl₃)

Assume the ionic compound dissociates 100%. The for eveary unit of AlCl₃ there will be 4 ions. Those are 4 particles and means that i = 4.

c) 3.0 M solution of ionic compound lithium bromide (LiBr)

Assuming also 100% dissociation of this ionic compound, since every LiBr unit dissociates into two ions, i = 2.

d) 3.0 M solution of ionic compound calcium fluoride (CaF₂)

Following same reasoning, i = 3.

5) Conclusion: since the greatest i factor is 4, and given all the other factors equal, the 3.0 M solution of ionic compound aluminum chloride (AlCl₃), option b, would be the aqueous solutions with the highest boiling point,

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2 years ago

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