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LekaFEV [45]
3 years ago
13

In 1838, botanist Matthias Schleiden, determined that all plants are composed of cells. In 1839, anatomist Theodor Schwann propo

sed that all animals are composed of cells. In 1855, biologist Rudolph Virchow added to Schleiden’s and Schwann’s observations and proposed that all living things are composed of cells. Which statement is also part of Virchow’s cell theory?
Chemistry
1 answer:
Margarita [4]3 years ago
6 0

Answer:

This question is incomplete; the complete part is:

A) All cell have a cell wall.

B) All cell arise from pre-existing cells.

C) All cell are capable of photosynthesis.

D) All cell can develop into any other type of cell.

The answer is B

Explanation:

The commonly known universal theory proposed in 1838 took the contribution from three remarkable scientists namely: botanist Matthias Schleiden, anatomist Theodor Schwann and biologist Rudolph Virchow. According to the question, Mathias discovered that all plants are made of cells, Schwann determined that all animals are made of cells while Virchow determined that all living things are composed of cells.

However, in addition to Virchow's discovery, he also discovered and proposed that "All cell arise from pre-existing cells", which till date forms part of the three components of the cell theory. The three parts are:

- Cell is the fundamental and basic unit of all living things.

- All living things are made up of one or more cells

- All cells arise from pre-existing cells

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Determine ΔH for the reaction CaCO3 → CaO + CO2 given these data: 2 Ca + 2 C + 3 O2 → 2 CaCO3 ΔH = −2,414 kJ C + O2 → CO2 ΔH = −
kicyunya [14]

Answer:

The ΔH for the reaction is -456.5 KJ

Explanation:

Here we want to determine ΔH for the reaction;

Mathematically;

ΔH = ΔH(product) - ΔH(reactant)

In the case of the first reaction;

ΔH = ΔH(CaO) + ΔH(CO2) - ΔH(CaCO3)  ...........................(*)

From the other reactions, we can get the respective ΔH for the individual molecule in the reaction

In second reaction;

Kindly note that for elements, molecule of gases, ΔH = 0

What this means is that throughout the solution;

ΔH(Ca)  = 0 KJ

ΔH(O2) = 0 KJ

ΔH(C) = 0 KJ

Thus, in writing the equation for the subsequent chemical reactions, we shall need to write and equate the overall ΔH for the reaction to that of the product alone

So in the second reaction

ΔH = 2ΔH(CaCO3)

Thus;

-2414/2 = ΔH(CaCO3)

ΔH(CaCO3) = -1,207  KJ

Moving to the third reaction, we have;

ΔH = ΔH(CO2)

Hence ΔH(CO2) = -393.5 KJ

For the last reaction;

ΔH = ΔH(CaO)

Hence ΔH(CaO) = -1270 KJ

Going back to equation *

ΔH = ΔH(CaO) + ΔH(CO2) - ΔH(CaCO3)

Using the values of the ΔH  of the respective molecules given above,

ΔH  = -1270 + (-393.5) - (-1207)

ΔH  = -456.5 KJ

8 0
3 years ago
When HClO2 is dissolved in water, it partially dissociates according to the equation
Natasha_Volkova [10]

Answer:

x = 100 * 1.1897 = 118.97 %, which is > 100 meaning that all of the HClO2 dissociates

Explanation:

Recall that , depression present in freezing point is calculated with the formulae = solute particles Molarity x KF

0.3473 = m * 1.86

Solving, m = 0.187 m

Moles of HClO2 = mass / molar mass = 5.85 / 68.5 = 0.0854 mol

Molality = moles / mass of water in kg = 0.0854 / 1 = 0.0854 m

Initial molality

Assuming that a % x of the solute dissociates, we have the ICE table:

                 HClO2         H+    +   ClO2-

initial concentration:       0.0854                    0             0

final concentration:      0.0854(1-x/100)   0.0854x/100   0.0854x / 100

We see that sum of molality of equilibrium mixture = freezing point molality

0.0854( 1 - x/100 + x/100 + x/100) = 0.187

2.1897 = 1 + x / 100

x = 100 * 1.1897 = 118.97 %, which is > 100 meaning that all of the HClO2 dissociates

3 0
3 years ago
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nataly862011 [7]

Answer: Each pair of shared electrons is a covalent bond which can be represented by a dash.

Explanation:

In a Lewis dot structure, the central atom can share electrons through bonds with the surrounding atoms, and this can look like a dash between the atoms.

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serious [3.7K]

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Answer:

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