Question

Part A

Estimate the number of moles of water in all the Earth's oceans. Assume water covers 75% of the Earth to an average depth of 3 km.

Express your answer to one significant figures and include the appropriate units.

Part B

Estimate the number of molecules of water in all the Earth's oceans.

Express your answer using one significant figure.

Part A Estimate the number of moles of water in all the Earth's oceans. Assume water covers 75% of the Earth to an average depth of 3 km. Express your answer to one significant figures and include the appropriate units. n-Value Units ane Submit My Answers Give Up Part B Estimate the number of molecules of water in all the Earth's oceans. Express your answer using one significant figure. molecules Submit My Answers Give Up

Answer 1

Part A.

We know that:

Molecular weight of water = 18 gm/mol = 18*10^-3 kg/mol

Number of moles = mass/Molecular weight

Mass of all the water on earth will be:

Mass = density*Volume

density of sea water = 1025 kg/m^3

Volume of water = 75% of Surface area of earth*depth of water = 0.75*4*pi*R^2*h

R = radius of earth = 6.371*10^6 m

h = depth of water = 3 km = 3000 m

So,

Volume = 0.75*4*pi*(6.371*10^6)^2*3000 = 1.1476*10^18 m^3

So,

Mass = 1025*1.1476*10^18 = 1.176*10^21 kg

Number of moles will be:

n = m/Mw

n = 1.176*10^21/(18*10^-3)

n = 6.533*10^22 moles

In one significant figures:

n = 7*10^22 moles

Part B.

Number of molecules of water will be:

N = n*Na

Na = Avogadro's number = 6.02*10^23 molescules

So,

N = 6.533*10^22*6.02*10^23

N = 3.933*10^46 molecules

In one signifcant figures:

N = 4*10^46 molecules

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