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3 years ago

Describe the results of a physical change and list three examples of physical change.

1 answer:

8 0

Physical changes are changes affecting the form of a chemical substance, but not its chemical composition. Physical changes are used to separate mixtures into their component compounds, but can not usually be used to separate compounds into chemical elements or simpler compounds.

Ex: cutting a paper, gaining weight, cutting hair

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What is the definition of a covalent bond?

kaheart [24]

A chemical bond that involves the sharing of electron pairs between atoms

8 0

3 years ago

Read 2 more answers

If the reaction of 150. G of ammonia with 150. G of oxygen gas yields 87. G of nitric oxide (no), what is the percent yield of t

Gekata [30.6K]

The percentage yield of the given reaction is 77.33%.

What is percentage yield?
Reactants frequently produce fewer product quantities than predicted by the chemical reaction's formula. The percentage of a theoretical yield that's been produced in a reaction is calculated using the percent yield formula. Working through a stoichiometry problem yields the theoretical yield, which is the ideal quantity of the final product. The actual yield is determined by calculating the volume of the product formed. We can determine the percentage yield by dividing the actual yield by the theoretical yield.

Moles is calculated by using the formula:
Moles of Ammonia:
Given mass of ammonia = 150g
Molar mass of ammonia = 17 g/mol
Putting values in above equation, we get:

Moles of Oxygen
Given mass of oxygen = 150g
Molar mass of oxygen = 32 g/mol
Putting values in above equation, we get:
For the given chemical equation:

By Stoichiometry,
5 moles of oxygen reacts with 4 moles of ammonia.
So, 4.6875 moles of oxygen will react with = of ammonia
As, moles of ammonia required is less than the calculated moles. Hence, ammonia is present in excess and is termed as excess reagent.
Therefore, oxygen is considered as a limiting reagent because it limits the formation of products.

By Stoichiometry of the given reaction:
5 moles of oxygen gas produces 4 moles of nitric oxide
So, 4.6875 moles of oxygen gas will produce = of nitric oxide

Now, to calculate the theoretical amount of nitric oxide, we use equation 1: Molar mass of nitric oxide = 30 g/mol
Given mass of nitric oxide = 112.5 g
Now, to calculate the percentage yield, we use the formula:
Experimental yield = 87 g
Theoretical yield = 112.5 g
Putting values in above equation, we get:
Hence, the percentage yield of the given reaction is 77.33%.

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6 0

1 year ago

A solution containing 8.3 g of a nonvolatile, nondissociating substance dissolved in 1.00 mol of chloroform, CHCl3, has a vapor

Margaret [11]

Answer:

a. Xm = 0.0229

b. 0.0234 moles

c. 354.1 g/mol

Explanation:

ΔP = P° . Xm

ΔP = P° - P', where P° is vapor pressure of pure solvent and P', vapor pressure of solution-

This is the formula for lowering vapor pressure.

If we apply the data given: 523 Torr - 511 Torr = 523 . Xm

Xm = ( 523 Torr - 511 Torr) / 523 Torr → 0.0229

Xm = Mole fraction of solute → Moles of solute / Total moles (sv + solute)

We can make this equation to determine moles of solute

0.0229 = Moles of solute / Moles of solute + 1

0.0229 (Moles of solute + 1) = Moles of solute

0.0229 = Moles of solute - 0.0229 moles of solute

0.0229 = 0.9771 moles of solute → 0.0229 / 0.9971 = 0.0234 moles

Molecular mass of solute → g/mol → 8.3 g / 0.0234 mol = 354.1 g/mol

7 0

3 years ago

Be sure to answer all parts. Consider the following balanced redox reaction (do not include state of matter in your answers): 2C

timurjin [86]

Answer:

The specie which is oxidized is:- $CrO_2^-$

The specie which is reduced is:- $ClO^-$

Explanation:

Oxidation reaction is defined as the chemical reaction in which an atom looses its electrons. The oxidation number of the atom gets increased during this reaction.

$X\rightarrow X^{n+}+ne^-$

Reduction reaction is defined as the chemical reaction in which an atom gains electrons. The oxidation number of the atom gets reduced during this reaction.

$X^{n+}+ne^-\rightarrow X$

For the given chemical reaction:

$2CrO_2^- + 6ClO^- + 2H_2O\rightarrow 2CrO_4^{2-} + 3Cl_2 + 4OH^-$

The half cell reactions for the above reaction follows:

Oxidation half reaction: $CrO_2^- + 2H_2O + 4OH^-\rightarrow CrO_4^{2-} + 4H_2O + 3e^-$

Reduction half reaction: $2ClO^- + 4H_2O + 2e^-\rightarrow Cl_2 + 2H_2O + 4OH^-$

Thus, the specie which is oxidized is:- $CrO_2^-$

The specie which is reduced is:- $ClO^-$

8 0

4 years ago

To indicate the pH of a substance, one can use a dye that is both an acid and that appears as different colors in its protonated

PIT_PIT [208]

Answer:

<em>The pH of the solution is 7.8</em>

Explanation:

The concentration of the solution is 0.001M and the dye could be in its protonated and deprotonated forms. If the concentration of the protonated form [HA] is 0.0002 M the concentration of the deprotonated form will be the subtraction between the concentration of the bye and the concentration of the protonated form:

[A-] = 0.001M - 0.0002M = 0.0008M

Also, the Henderson-Hasselbalch equation is

$pH = pKa + Log \frac{[A^{-}]}{[HA]}$

this equation shows the dependency between the pH of the solution, the pKa and the concentration of the protonated and deprotonated forms. Thus, replacing in the equation

$pH = 7.2 + Log \frac{0.0008M}{0.0002M} = 7.8$

3 0

3 years ago