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3 years ago

The Heliocentric model is when the sun, planets, and stars are orbiting a stationary Earth.

1 answer:

3 0

False

A heliocentric is when the model is
representing the sun as the center
A geocentric says the earth is at the center of the universe

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A scientist measures the standard enthalpy change for the following reaction to be 67.9 kJ:

bekas [8.4K]

Answer: The standard enthalpy of formation of $H_2O(g)$ is -252.1 kJ/mol.

Explanation:

The balanced chemical reaction is,

$Fe_2O_3(s)+3H_2(g)\rightarrow 2Fe(s)+3H_2O(g)$

The expression for enthalpy change is,

$\Delta H=[n\times H_f_{products}]-[n\times H_f_{reactantss}]$

Putting the values we get :

$\Delta H=[2\times H_f{Fe}+3\times H_f{H_2O}]-[1\times H_f{Fe_2O_3}+3\times H_f{H_2}]$

$67.9kJ=[(2\times 0)+(3\times H_f{H_2O})]-[(1\times -824.2kJ/mol)+3\times 0kJ/mol)]$

$H_f{H_2O}=-252.1kJ/mol$

Thus standard enthalpy of formation of $H_2O(g)$ is -252.1 kJ/mol.

3 0

3 years ago

An astronaut has a mass of 60kg. Calculate their weight When they are on the surface of the moon.

IceJOKER [234]

Answer:

I think 0kg because they are flying.

7 0

3 years ago

Whats the largest watershed

Firdavs [7]

In the U.S.A, it is the Mississippi River Basin. But then there is the Gulf of Mexico.

6 0

3 years ago

How many outer rings does iodine have

Daniel [21]

53 if your talking about electrons. 74 if your talking about neutrons. energy levels=5 Hope this helps☺️

3 0

3 years ago

Which best demonstrates an example of the common ion effect?

ella [17]

Answer: A. The compound CuCl is 500 times less soluble in sea water than it is in pure water.

pure water.

Explanation:

Any change in the equilibrium is studied on the basis of Le-Chatelier's principle.

This principle states that if there is any change in a equilibrium reaction, the equilibrium will shift in a direction so as to minimize the effect.

Thus when a common ion is introduced to an equilibrium reaction, the equilibrium will shift in a direction where the concentration of common ion is decreasing.

$CuCl\rightleftharpoons Cu^++Cl^-$

$NaCl\rightarrow Na^++Cl^-$

When common ion such as $Cl^-$ from NaCl in sea water is introduced to an equilibrium reaction, the equilibrium will shift in a direction where the concentration of common ion is decreasing i.e. in the left side and thus solubility of CuCl further decreases.

6 0

3 years ago