We can also use the equation for enthalpy change for physical phase changes. Consider the phase change H2O(l) → H2O(g). Calculate ΔHrxn.Use ΔHf values from the table above.

ΔHrxn = _____

Answer:

percent by mass = 79%

Explanation:

Data Given:

mass of solute (Na₂CO₃) = 75 g

mass of solvent ( water ) = 20 g

mass percent of solution = ?

Solution:

Formula used to find percent by mass

                          mass of solute / mass of solution x 100 . . . . . . (1)

first we have to find mass of solution

              mass of solution = mass of solute + mass of Solvent . . . . (2)

put values in equation 2

             mass of solution = 75 g + 20 g

             mass of solution = 95 g

Now,

put values in equation 1

 Percent by mass = mass of solute / mass of solution x 100

 Percent by mass = 75 g / 95 g x 100

 Percent by mass = 79 %

so,

The percent of the solution by mass = 79%

***Note:

The same work can be used for the other values too i.e. if you have 20 g of solute and 75 g solvent.

Answer:

The answer is 78.9%

Explanation:

The percentage weight in volume indicates the mass of solute per volume. We will use the% weight/volume formula to calculate what the exercise asks for, as follows:

%

The main cause of rising the surface temperature of the pacific ocean drought in the western united states, and flooding on the pacific coast of south america is the phenomenon called El-nino.

What is El-nino ?

Surface temperatures in the equatorial Pacific rise during El Nino, while the east-west trade winds that blow close to the equator diminish. Typically, trade winds from the Americas move eastward towards Asia.

They sputter and alter course because of El Nino, becoming westerlies and carrying warm water from the western Pacific to the Americas.

Deeper seas are typically nutrient-richer, however under El Nino upwelling is limited, which reduces phytoplankton along the coast. Deeper waters typically rise to the surface.

Fish that consume phytoplankton are the first to be impacted, then organisms farther up the food chain. Additionally, tropical animals are transported by warmer water to colder regions, upsetting numerous ecosystems.

To find more on El-Nino, refer here:

brainly.com/question/28301099

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What is the cause of rising surface temperatures of the pacific ocean, drought in the western united states, and flooding on the pacific coast of south america?

The cause of rising surface temperatures of the pacific ocean, drought in the western united states, and flooding on the pacific coast of south America is the carbon – producing companies.

Answer:

Magnet

Durability and heaviness.(texture)

Explanation:

Magnet can be use to separate Aluminum from mixture of steel and aluminum.

Though aluminum and steel look alike but magnet can be use to separate it.

If the can attract the magnet or magnet stick to the can, it is a steel can. Aluminum does not stick to magnet.

A mixture of Aluminum and tin can also be separated by magnet.

Tin attract magnet but tin is more durable, heavy and does not corrode easily.

When u touch the three cans, tin is heavy and durable.

Answer : Option A) HF.

Explanation : Assuming the complete question as per the attachment.

H-F bonds are formed because of hydrogen bonding between H atom and F atom and is considered to be strongest amongst the rest other options given.

As given in the table it is clear that the molar mass of HF molecule is the lowest. It shows that, when dispersion increases in the molecule molecular weight also increases.