1. How many grams of zinc are in 300.0 moles of zinc?
2. How many grams of chlorine are in 25.6 moles of chlorine? (Cl2)
3. How many moles of carbon in 25.6 g of carbon?
4. How many moles of sodium are in 26.5 g of sodium?
5. How many grams of sodium are in 5.60 x 10 23 atoms of sodium? (This is a two step equation)

(Show Work)

Explanation:

The problems are very similar and we will apply the mole concepts to solve them and obtain an accurate answer

1. How many grams of zinc are in 300.0 moles of zinc?

Given parameters:

Number of moles of Zn = 300moles

Unknown:

Mass of zinc  = ?

Solution;

The number of moles is related to mass using the expression below;

             Mass of a substance  = number of moles x molar mass

The mole is standard quantity used in chemical measurements in the laboratory.

   Molar mass of Zn  = 65.4g/mol

       Mass of zinc  = 300 x 65.4  = 19620g

2. How many grams of chlorine are in 25.6 moles of chlorine? (Cl₂)

Given parameters:

Number of moles of Chlorine gas  = 25.6moles

Unknown:

Mass of Chlorine = ?

Solution:

Here we are dealing with chlorine gas, a covalent molecule. The expression that relates mass to number of moles will be used to solve this problem;

           Mass = number of moles x molar mass

 Molar mass of Cl₂  = 2 x35.5  = 71g/mol

   input the parameters;

           Mass  = 25.6 x 71  = 1817.6g

3. How many moles of carbon in 25.6 g of carbon?

Given parameters:

Mass of carbon = 25.6g

Unknown:

Number of moles  = ?

Solution:

Here we are solving for the number of moles. We are going to use the expression that relates the number of moles to mass to solve this problem.

       Number of moles  =

 Molar mass of C  = 12g/mol

  Input the parameters;

                Number of moles  =   = 2.13moles

4. How many moles of sodium are in 26.5 g of sodium?

Given parameters:

Mass of Na  = 26.5g

Unknown:

Number of moles of Na  = ?

Solution:

Since mass is given, using the periodic table we can ascertain the molar mass of Na and we plug into the expression below to find the number of moles;

             Number of moles  =

molar mass of Na  = 23g/mole

          Number of moles  =   = 1.15moles

5. How many grams of sodium are in 5.60 x 10 23 atoms of sodium? (This is a two step equation)

Given parameters:

Number of atoms of Na  = 5.6 x 10²³atoms

Unknown:

Mass of Na = ?

Solution:

To solve this problem, we have to relate the number of moles to mass and the number of atoms.

  1 mole of a substance  = 6.02 x 10²³atoms

First we find the number of moles from this relationship above;

             6.02 x 10²³atoms    = 1 mole

              5.6 x 10²³atoms  =    = 0.93moles of Na

Also;

      Mass of a substance  = number of moles x molar mass

molar mass of Na  = 23g/mol

          Mass of Na  = 0.93 x 23  = 21.39g

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explanation:

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"standard molar enthalpy:

h2o ( liquid water ) : - 285.8 kj/mole

h2o ( water vapor ) : - 241.8 kj / mole.

δhrxn = - 241. 8 - ( - 285.8 )= -241.8 + 285.8 = 44.0

answer: 44.0 kj"