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inessss [21]
4 years ago
6

When did oxygen first appear in earth's atmosphere??

Chemistry
1 answer:
ad-work [718]4 years ago
7 0
<span> the atmosphere holds about 21 per cent oxygen. Over the Earth’s 4.6 billion year history, oxygen did not appear in the atmosphere until perhaps about 2.5 billion years ago. Since then, oxygen levels have fluctuated in tandem with global geological and biological events, such as mass extinctions.</span>
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Formula D = m / V m = 22 g D = 4 g/mL What is the Volume of the object in mL? Do not include the units in your answer.
Lemur [1.5K]

Answer:

The answer is

<h2>5.50</h2>

Explanation:

The volume of a substance when given the density and mass can be found by using the formula

volume =  \frac{mass}{density}  \\

From the question

mass = 22 g

density = 4 g/mL

The volume is

volume =  \frac{22}{4}  =  \frac{11}{2}  \\

We have the final answer as

<h3>5.50 mL</h3>

Hope this helps you

6 0
3 years ago
What is the mass of 2 moles of 238 u?
Ad libitum [116K]
<span>use this formula mass = moles x molar mass</span>
5 0
3 years ago
Read 2 more answers
The pH scale:
faltersainse [42]
It runs from 0 to 14. (A)

It is based off the -log [H+] where [H+] is the concentration of the Hydrogen ions.
5 0
3 years ago
Read 2 more answers
A solution containing 0.050 g of an unknown nonelectrolyte in 2.50 g of cyclohexane (Kf = 20.4 oC/m &amp; F.P. 6.6 oC) was found
ANEK [815]

Answer:

The molar mass of the unknown substance is 255g/mole

Explanation:

Freezing point depression is given by

ΔT = i · Kf · m

Where

m = molality of the solute

i = van't Hoff's factor = i for non electrolyte

Kf = 20.4 °C/m = cryoscopic constant

ΔT = Freezing point depression

Therefore ΔT = 6.6 - 5 = 1.6 °C

1.6 °C = 20.4 °C/m × 1 × m

Therefore m = 1.6/20.4 = 0.0784 m

number of moles in 2.50 g of cyclohexane = 0.0784 m or 0.0784 moles of the substance in 1000 grams of cyclohexane. That is

2.5 ×0.0784/1000 moles in 2.5 graams of cyclohexane  that is

1.96 × 10⁻⁵ moles in 2.5 grams of cyclohexane

1.96 × 10⁻⁵ moles of the substance weighs 0.050 grams

Therefore 1 Mole weighs (0.05 g)/(1.96 × 10⁻⁵ moles) = 255g/mole

7 0
3 years ago
The reactivity of elements can be predicted based on the position of an element in the periodic table. Based on the periodic tab
Viefleur [7K]

Answer:

Chlorine (Cl) is most reactive out the the listed elements.

4 0
3 years ago
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