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3 years ago

Salt dissolves in water because salt is held together by:

1 answer:

mote1985 [20]3 years ago

7 0

Water can dissolve salt because the positive part ofwater molecules attracts the negative chloride ions and the negative part of water molecules attracts the positive sodium ions. The amount of a substance that candissolve in a liquid (at a particular temperature) is called the solubility of the substance.

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If 8.50 g of phosphorus reacts with hydrogen gas at 2.00 atm in a 10.0-L container at 298 K, calculate the moles of PH3 produced

ahrayia [7]

Answer:

The moles of PH₃ produced are 0.2742 and the total number of moles of gas present at the end of the reaction is 0.6809.

Explanation:

Phosphorus reacts with H₂ according to the balanced equation:

P₄ (s) + 6 H₂ (g) ⇒ 4 PH₃ (g)

By stoichiometry of the reaction (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of each compound participate in the reaction:

P₄: 1 mole
H₂: 6 moles
PH₃:4 moles

Being the molar mass of the compounds:

P₄: 124 g/mole
H₂: 2 g/mole
PH₃: 34 g/mole

The following mass amounts of each compound participate in the reaction:

P₄: 1 mole* 124 g/mole= 124 g
H₂: 6 mole* 2 g/mole= 12 g
PH₃: 4 moles* 34 g/mole= 136 g

An ideal gas is characterized by three state variables: absolute pressure (P), volume (V), and absolute temperature (T). The relationship between them constitutes the ideal gas law, an equation that relates the three variables if the amount of substance, number of moles n, remains constant and where R is the molar constant of the gases:

P * V = n * R * T

In this case you know:

P= 2 atm
V= 10 L
n= ?
R= 0.082 $\frac{atm*L}{mol*K}$
T= 298 K

Replacing:

2 atm*10 L= n*0.082 $\frac{atm*L}{mol*K}$ *298 K

and solving you get:

$n=\frac{2 atm*10 L}{0.082\frac{atm*L}{mol*K}*298 K }$

n=0.818 moles

The limiting reagent is one that is consumed first in its entirety, determining the amount of product in the reaction. When the limiting reagent is finished, the chemical reaction will stop.

To determine the limiting reagent, you can use a simple rule of three as follows: if 6 moles of H₂ react with 124 g of P₄, 0.818 moles of H₂ with how much mass of P₄ will it react?

$mass of P_{4}=\frac{0.818 moles of H_{2}*124 grams of P_{4}}{6 moles of H_{2}}$

mass of P₄= 16.90 grams

But 16.90 grams of P₄ are not available, 8.50 grams are available. Since you have less mass than you need to react with 0.818 moles of H₂, phosphorus P₄ will be the limiting reagent.

Then you can apply the following rules of three:

If 124 grams of P₄ produce 4 moles of PH₃, 8.50 grams of P₄, how many moles do they produce?

$moles of PH_{3} =\frac{8.5 grams of P_{4}*4 moles of PH_{3} }{124grams of P_{4}}$

moles of PH₃=0.2742

If 124 grams of P₄ react with 6 moles of H₂, 8.50 grams of P₄ with how many moles of H₂ do they react?

$moles of H_{2} =\frac{8.5 grams of P_{4}*6 moles of H_{2} }{124grams of P_{4}}$

moles of H₂= 0.4113

If you have 0.818 moles of H₂, the number of moles of gas H₂ present at the end of the reaction is calculated as:

0.818 - 0.4113= 0.4067

Then the total number of moles of gas present at the end of the reaction will be the sum of the moles of PH₃ gas and H₂ gas that did not react:

0.2742 + 0.4067= 0.6809

Finally, the moles of PH₃ produced are 0.2742 and the total number of moles of gas present at the end of the reaction is 0.6809.

5 0

2 years ago

ddt, dde, pcbs and pbdes are all ________ddt, dde, pcbs and pbdes are all ________.a biodegradable and do not persist in the env

qwelly [4]

The answer is non-biodegradable and subject to bioaccumulation and/or bioamplification.

DDT (dichlorodiphenyltrichloroethane) is persistent, non-degradable insecticide and organic pollutant readily accumulated to soils and consequently affects organisms.
DDE (dichlorodiphenyldichloroethylene) is non-degradable pesticide toxic to birds at the first place.
PCBs (polychlorinated biphenyls) are non-degradable organic compounds very toxic to the environment.
PBDEs (polybrominated diphenyl ethers) are non-degradable compounds very toxic to environment, even able to affect brains of animals in the development period.

5 0

3 years ago

how do the properties of compounds compare to the properties of the elements from which they are composed

Crank

The elements that form the compound don't compare because it doesn't matter about the elements when they are combined. The elements that formed it together is completely different than the outcome compound.

6 0

2 years ago

Consider the following specific heats: copper, 0.384 J/g· ◦C; lead, 0.159 J/g· ◦C; water, 4.18 J/g· ◦C; glass, 0.502 J/g· ◦C. Wh

Roman55 [17]

Answer:

The correct answer is

2. Water

Explanation:

The specific heat capacity is the amount of heat required to raise the temperature of a unit mass of a substance by one degree. It is connected to the capacity of the substance to retain heat as well as the rate at which it will cool down or heat up when exposed to a specific amount of heat loss or heat supplied. A substance with a low heat capacity such as iron will cool down or heat up more quicker than a substance with a high heat capacity such as water.

From the list of substances water has the highest heat capacity, (4.18 J/g) as such it will retain heat for the longest period of time.

7 0

2 years ago

Look up and record the boiling point of acetic acid, and explain why only some of it evaporates from the reaction mixture.

REY [17]

Answer:

Heating the mixture to a temperature above the boiling point of acetic acid, but below 100°C (the boiling point of water). The vapours from the acetic acid rise, and go into a tube. They are then condensed within the tube, and run off into a separate storage area. Because water can exist as a gas at pretty much any temperature above 0°C, it will result in an impure mixture, but repeatedly doing this will get the acetic acid to the desired purity.

8 0

3 years ago