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3 years ago

According to scientific evidence, earth’s earliest atmosphere lacked oxygen. Over time, oxygen was added to the atmosphere.

1 answer:

4 0

B.
The cynobacteria were already there without the oxygen, so that rules out A, and a lot of prokaryotes were anaerobic, so that rules out C. Finally, Photosynthesis does not require oxygen. Instead, Oxygen is a waste product of it. Therefore, it cannot be D. So, we are only left with B
Hoped this helped :D

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A propane stove burned 470 grams propane and produced 625 grams of water (this is the actual yield) C3H8 +5O2=3CO2+4H20. What wa

Liula [17]

Answer:

81.3%

Explanation:

Step 1:

The balanced equation for the reaction:

This is shown below:

C3H8 + 5O2 —> 3CO2 + 4H2O

Step 2:

Data obtained from the question. This includes:

Mass of propane (C3H8) = 470 g

Actual yield of water (H2O) = 625 g

Percentage yield of water (H2O) =?

Step 3:

Determination of the mass of propane (C3H8) burned and the mass of water (H2O) produce from the balanced equation. This is illustrated below:

C3H8 + 5O2 —> 3CO2 + 4H2O

Molar Mass of C3H8 = (3x12) + (8x1) = 36 + 8 = 44g/mol

Molar Mass of H2O = (2x1) + 16 = 2 + 16 = 18g/mol

Mass of H2O from the balanced equation = 4 x 18 = 72g

From the balanced equation above,

44g of C3H8 was burned and 72g of H2O was produced.

Step 4:

Determination of the theoretical yield of H2O. This is illustrated below:

From the balanced equation above,

44g of C3H8 produced 72g of H2O.

Therefore, 470g of C3H8 will produce = (470x72)/44 = 769.09g of H2O.

Therefore, the theoretical yield of H2O is 769.09g

Step 5:

Determination of the percentage yield of water (H2O). This is illustrated below:

Actual yield of water (H2O) = 625g

theoretical yield of H2O = 769.09g

Percentage yield of water (H2O) =?

Percentage yield = Actual yield/Theoretical yield x100

Percentage yield = 625/769.09 x100

Percentage yield = 81.3%

Therefore, the percentage yield of water (H2O) is 81.3%

4 0

4 years ago

How can you which molecule is positive and negative in a dipole-dipole relationship?

marysya [2.9K]

Dipole interactions are observed in covalent bonds. In ionic bonding, permanent transfer of electrons occurs and due to this dipole-dipole interactions are not observed. In covalent bonding, electron cloud is shared between 2 atoms. If this electron cloud is not shared equally between them, polarities are formed in a molecule. And hence we say that the molecule is polar. For a molecule to be polar, there should be electronegativity difference between them. Atom with greater electronegative attracts electron cloud more towards itself whereas atom with lesser electronegative attracts electron cloud less. But there is no permanent transfer of electrons. Due to this electronegativity differences, atom with more electronegative gains partial negative charge and atom with lesser electronegative value gains partial positive charge. The charge is partial because there is no complete transfer of electrons.

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4 years ago

Students in a chemistry class are drawing molecular models based on molecular formulas they are given by the teacher.

Karo-lina-s [1.5K]

Sorry I need this marks

5 0

3 years ago

Which type of rock forms as a result of cooling and crystallization?

Dovator [93]

Answer:

Igneous rock is the type of rock that forms as a result of cooling an crystallization

Explanation:

Rocks are either sedimentary, igneous or metamorphic based on the chemical composition and the mode of formation.
Igneous rocks are formed as a result of the cooling and crystallization of magma from volcanic eruptions.
Igneous rocks are either intrusive, which form deep in the crust or extrusive which form on the surface of the earth.
Sedimentary rocks are formed as a result of deposition, and cementation of sediments.
Metamorphic rocks, on the other hand, are formed from the sedimentary and igneous rocks during the rock cycle.

7 0

3 years ago

Most of the water a vascular plant takes in ______. Goes back into the soil Evaporates in the process of transpiration Is used t

MatroZZZ [7]

Answer:

EVAPORATES IN THE PROCESS OF TRANSPIRATION

Explanation:

Plants takes in water from the soul via it's root system. Small amount of the water are used for growth and metabolism of the plants. Some are used in the process of photosynthesis. The bulk of the remaining are lost through transpiration. This takes place in the stomata of the plants. The stomata are numerous on the leaf surfaces and are guarded by cells which allow for opening and closing of the stomata. Transpiration helps the plants to remove CO2 produced by photosynthesis, cools the plant and also changes osmotic pressure of the plant which allows for the flow of nutrients and water from the root to the leaves, flowers, fruits.

7 0

3 years ago