You must know and use the formula for pH.
pH = - log [H3O+], where [H3O+] is the molar concentration of hydronium ion.
So, when pH is 8.0 => 8.0 = - log [H3O+] and you can use antilogarithm (the inverse function of logarithm) to find [H3O+], in this way:
[H3O+] = 10^-8 = 1 * 10 ^-8 M
When, pH = 7.0 =>
7.0 = - log [H3O+] => [H3O+] = 1 * 10^ -7 M
Answer: 1*10^-7 mole / liter
The Earth, Mars or Jupiter should be denser than the Sun. Density is defined by mass and volume — components of object or matter. Although the sun is huge, it’s component is made up of mostly gas (hydrogen and helium). While Earth, though smaller than the Sun, contains heavier elements such as iron, sulfur, rocks, sediments, granite, basalt and water. Mars (composed of rocks and nutrients) and Jupiter (contains gases and compounds) as well are denser when compared to the Sun’s density. Referencing to our basic understanding of matter: solid and liquid should be heavier than gas.
Answer:
I think it should be Carbon.
When 440.23 grams of iron(III) oxide are reacted with hydrogen gas, the amount of iron produced will be 307.66 grams
<h3>Stoichiometric calculation</h3>
From the equation of the reaction:

The mole ratio of iron(III) oxide to produced iron is 1:2.
Mole of 440.23 iron(III) oxide = 440.23/159.69 = 2.76 moles
Equivalent mole of produced iron = 2.76 x 2 = 5.52 moles
Mass of 5.52 moles of iron = 5.52 x 55.8 = 307.66 grams
More on stoichiometric calculations can be found here; brainly.com/question/27287858
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Nonfoliated is the answer I belive.. Hopefully