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valentina_108 [34]
2 years ago
14

For hundreds of years, people believed that life forms could just appear. That is because they could not see microscopic organis

ms. In 1859, Louis Pasteur performed an important experiment that proved there were small, unseen bacteria in the air that caused milk to sour and food to rot. He later linked that to unseen organisms that also cause disease. To which part of the Cell Theory did Pasteur make the biggest contribution? A) Cells are the basic units of life. B) All organisms are composed of cells. C) All cells come from pre-existing cells. D) Cells contain DNA which is found specifically in the chromosome
Chemistry
1 answer:
creativ13 [48]2 years ago
6 0

Answer:

Actually,the answer is C

Explanation:

All cells come from pre-existing cells.

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3 years ago
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Two solutions, initially at 24.60 °C, are mixed in a coffee cup calorimeter (Ccal = 15.5 J/°C). When a 100.0 mL volume of 0.100
yulyashka [42]

Answer:

ΔH = -59.6kJ/mol

Explanation:

The reaction that occurs between Ag⁺ and Cl⁻ ions is:

Ag⁺ + Cl⁻ → AgCl(s) + ΔH

To find ΔH we need to obtain moles of reaction and heat released in the reaction because ΔH is defined as heat released per mole of reaction.

<em>Moles of reaction:</em>

Moles of Ag⁺ and Cl⁻ added are:

Ag⁺: 0.100L * (0.100mol / L) = 0.01moles

Cl⁻: 0.100L * (0.200mol / L) 0 0.02 moles

That means limiting reactant is Ag⁺ and moles of reaction are 0.01 moles

<em>Heat released:</em>

To find heat released we must use coffe cup calorimeter equation:

Q = C*m*ΔT

<em>Where C is specific heat of solution (4.18J/g°C), m is the mass of solution (200g because there are 100 + 100mL = 200mL and density of solution is 1g/mL) and ΔT is change in temperature (25.30°C - 24.60°C = 0.70°C).</em>

Replacing:

Q = C*m*ΔT

Q = 4.18J/g°C * 200g * 0.70°C

Q = 585,2J

Is total heat released.

The calorimeter absorbs:

15.5J / °C * 0.7°C = 10.85

Thus, when 0.01 moles reacts, 585.2J + 10.85  = 596.05J are released (Heat released is heat abosrbed by calorimeter + Heat absorbed by water) and ΔH is:

ΔH = 596.05J / 0.01 moles =

ΔH = 59605J / mol =

<h3>ΔH = -59.6kJ/mol</h3>

<em>As heat is released, ΔH < 0.</em>

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C: This is also a physical change because the water is just dragging sand with it, but not actually changing the composition of it.

D: Similar to option B, this is an example of physical weathering because the ice only divides the rock into different parts but doesn't change the composition or complexity of it.

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