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(worth 10pts!!!!!!) What did Dmitri Mendeleev contribute to science? A. He arranged the first periodic table. B. He developed th

vesna_86 [32]

Answer:

A. He arranged the first periodic table.

Explanation:

3 0

3 years ago

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The density of water at 400C is 0.992 g/mL What is the volume of 27.0 g of water at this temperature?

pantera1 [17]

Answer:

Volume of water at this temperature is 27.2 mL

Explanation:

We know that $density=\frac{mass}{volume}$

Here density of water is 0.992 g/mL

Here mass of water is 27.0 g

So $volume=\frac{mass}{density}$

= $\frac{27.0g}{0.992g/mL}$

= 27.2 mL

7 0

3 years ago

Through which of the following processes is carbon directly transferred between living organisms and the environment?

sertanlavr [38]

Answer:

The answer is carbon cycle.

Explanation:

The carbon cycle is an important process for living organisms. As plants prepare their food through photosynthesis and is also an important source of fossil fuels for human activities.

Therefore carbon atoms are regenerated again and again in the carbon cycle process. This recycling process takes place between livings and nonliving things in the environment and also within the earth biosphere.

Abundance supply of carbon is necessary to carry out the biological processes. The entire carbon cycle is actually made up of sourced and sinks elements.

4 0

3 years ago

Photosynthesis by land plants leads to the fixation each year of about 1 kg of carbon on the average for each square meter of an

Rama09 [41]

Answer:

a) mass of carbon directly above 1 ( each) square meter of the earth is 1.65kg

b) all CO₂ will definitely be used up from the atmosphere directly above a forest in 1.65 years

Explanation:

first we calculate the moles of carbon

moles = mass/molar mass

= 1kg/12gmol⁻¹

= 1000g/12gmol⁻¹

= 83.33 mol

now using the ideal gas equation

we find the volume of co₂required based on 83.33 moles

PVco₂ = nRT

Vco₂ = nRT/P

Vco₂ = (83.22mol × 0.0821L atm k⁻¹ mol⁻¹ 298 K) / 1 atm

Vco₂ = 2083.73 L

so since CO₂ in air is 0.0390% by volume in the atmosphere, we find the the total amount of air required to obtain 1kg carbon

therefore

Vair × 0.0390/100 = 2038.73L

Vair = (2038.73L × 100) / 0.0390

Vair = 5.23 × 10⁶L

therefore 5.23 × 10⁶ L of air will be required to obtain 1kg carbon

a)

Here we calculate the mass of air over 1 square meter of surface.

Remember that atmospheric pressure is the consequence of the force exerted by all the air above the surface; 1 bar is equivalent to 1.020×10⁴kgm⁻²

NOW

mass of air = 1.020×10⁴kgm⁻² × 1m²

= 1.020×10⁴kg

= 1.020×10⁷g [1kg = 10³g]

we now find the moles of air associated with it

moles = mass/molar mass

= 1.020 × 10⁷g / ( 20%×Mo₂ + 80%×Mn₂)

= 1.020 × 10⁷g / ( 20%×32gmol⁻¹ + 80%×28gmol⁻¹)

= 1.020 × 10⁷g / 28.8 gmol⁻¹

= 354166.67mol

so based on the question, for each mole (air), there is 0.0390% of CO₂

now to calculate the moles of CO₂ we say;

MolesCo₂ = 0.0390/100 × 354166.67mol

= 138.125 moles

Now we calculate mass of CO₂ from the above findings

Moles = mass/molar mass

mass = moles × molar mass

= 138.125 moles × 12gmol⁻¹

= 1657.5g

we covert to KG

= 1657.5g / 1000

mass = 1.65kg

therfore mass of carbon directly above 1 ( each) square meter of the earth is 1.65kg

b)

to find the number years required to use up all the CO₂, WE SAY

Number of years = total carbon per m² of the forest / carbon used up per m² from the forest per year

Number of years = 1.65kgm⁻² / 1kg²year⁻¹

Number of years = 1.65 years

Therefore all CO₂ will definitely be used up from the atmosphere directly above a forest in 1.65 years

6 0

3 years ago

Which of the following statements about enthalpy is true?

Evgesh-ka [11]

Answer: A chemical process must occur and then changes between the state of the reactants and the state of the products can be determined

Explanation: Enthalpy represents the sum of the energy of the system with the product of the pressure and volume of that system. As a thermodynamic property, it expresses the ability to release heat from the system. In fact, enthalpy tells us how much heat and work has changed during the chemical reaction under constant pressure. When measuring, measurements of the difference in enthalpy between the two states of the system is performed, before and after the chemical reaction, since total enthalpy can not be measured. This measurement of the enthalpy change can tell us, for example, whether the heat was released from the system during the reaction, or the system absorbed the heat.

7 0

3 years ago