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3 years ago

Which of the following is not an element that makes up all living organisms?

Chemistry

1 answer:

Bess [88]3 years ago

8 0

Answer: Rubidium is correct

Explanation: The six most common elements in living things are carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur. Atoms of these elements combine and form thousands of large molecules. These large molecules make up the structures of cells and carry out many processes essential to life.

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Identify each description as either a physical or chemical change.

Anettt [7]

Answer:

1 - physical

2 -chemical

3 - chemical

4 - physical

5 - physical

6 - chemical

7 - physical

8 - chemical

4 0

3 years ago

Briefly describe how a potentiometric pHmeter works. (Hint: Describe how the pH meter measures the amount of H+ or OH- ions in a

KengaRu [80]

Answer:

Indicators show changes in the pH of a solution

Explanation:

A pH meter is an instrument that measures the hydrogen-ion activity in aqueous solutions, indicating the acidity or alkalinity of the solution expressed as pH .The pH meter measures the difference in electrical potential between a pH electrode and a reference electrode, hence the pH meter is sometimes referred to as a potentiometric pH meter. Potentiometric pH meters measure the voltage between two electrodes and display the result converted into the corresponding pH value. The instrument comprises of a simple electronic amplifier and a pair of electrodes, or alternatively a combination electrode, and some form of display calibrated in pH units. It usually has a glass electrode and a reference electrode, or a combination electrode. The electrodes, or probes, are inserted into the solution to be tested.

Organic indicators are chemical species that change their colour in response to changes in the pH of the solution. This implies that the anionic and protonated forms of the indicator possess different colours. Hence the colour changes in acidic, basic and neutral solutions. The images attached indicate the colour changes in phenolphthalein and methyl orange in acidic and basic media accordingly.

4 0

2 years ago

How does a greenhouse keep radiant energy from escaping?

Rina8888 [55]

Greenhouse effect is the process of trapping sun radiation in the earth surface, so as to make the planet warm. It is a natural phenomenon in which sun rays that enters the earth surface are re-radiated into the earth surface causing the heat trap in the earth.
In similar manner, green house also trap radiation inside the glass house. The sun rays once reach inside the glass house, strike on plants and objects and reflected back. For entire radiation to escape from the green house, the heat flow between the two points must be proportional to the temperature difference and thermal conductivity. The glass of which the green house are made up, have low thermal conductivity. So, temperature must rise inside glass house so to maintain the heat flow rate of incoming and outgoing radiation.
The green house glass are insulated and they trap the infrared emitted by the objects inside the green house from escaping outside. Since the infrared have longer wave lengths, it is released slowly.

Also, the thermal energy inside the glass house are transferred by convection process. But the glass walls and roof act as insulator, keeping the radiant energy from escaping outside the green house.

7 0

3 years ago

Calculate the osmotic pressure associated with 50.0 g of an enzyme of molecular weight 98 g/mol dissolved in water to give 2600

andrew-mc [135]

Answer:

π = 4,882 atm

Explanation:

To calculate the osmotic pressure (π), the Van´t Hoff equation must be used, which is:

π x V = n x R x T

Where:

• π: Osmotic pressure, which is the difference between the levels of the solution and the pure solvent through a semipermeable membrane, which allows the passage of the solvent but not the solute

• V: Volume of the solution, in liters unit

• n: Number of moles of solute

• R: Constant of ideal gases, equal to 0.08206 L.atm / mol.K

• T: Absolute temperature, in Kelvin degrees

With the data you provide you can calculate the osmotic pressure by clearing it from the equation, we would be equal to:

π = (n x R x T) / V

However, all data must first be converted to the corresponding units in order to replace the values in the equation.

Solution volume ⇒ go from mL to L: 

1000 mL of solution ____ 1 L

2600 mL of solution _____ X = 2.6 L

Calculation: 2600 mL x 1 L / 1000 mL = 2.6 L

Temperature ⇒ Go from ° C to K 

T (K) = t (° C) + 273.15 = 30.0 ° C + 273.15 = 303.15 K

Number of moles of solute ⇒ It can be calculated since we have the mass of the enzyme and its molecular mass:

98.0 g of enzyme ____ 1 mol

50.0 g of enzyme _____ X = 0.510 moles

Calculation: 50.0 g x 1 mol / 98.0 g = 0.510 moles

Now, you can replace the values in the Van´t Hoff equation and you will get the result:

π = (n x R x T) / V

π = (0.510 mol x 0.08206 L.atm / mol.K x 303.15 K) / 2.6 L = 4.882 atm

Therefore, the osmotic pressure will be 4,882 atm

3 0

3 years ago

Explain why it is advantageous that water does not evaporate quickly on earth PLEASE HELP!!

stich3 [128]

Answer:

When the humidity is 100 percent, the air is saturated with water. Air pressure also affects evaporation. If air pressure is high on the surface of a body of water, then the water will not evaporate easily. The pressure pushing down on the water makes it difficult for water to escape into the atmosphere as vapor.

Explanation:

6 0

2 years ago