Find the enthalpy change per mole of sodium when sodium reacts with water. 13 grams of sodium reacts with 247 cm3 of water, producing a temperature change from 298 k to 339.7 k. the specific heat capacity of water is 4.18 j/k g.

The answer is

-79 kJ/mol

The explanation:

The reaction equation is:

2Na + 2H2O  2NaOH + H2

when ΔHrxn= -q

and q=cmΔT

where:

-q is amount of heat absorbed/released

-and c is specific heat of solution (in such calculation an assumption is made that c solution =   c water)        

- and m is mass of solution

- and ΔT is temperature change

1- now we need to Find mass of solution:

m solution = m(H2O)+ m(Na)-m(H2)m(H2O)

m H2O= V(H2O)*ρ(H2O)

             = 247 cm3*1g/cm3 = 247 gm

and m(Na)= 13 g

2- now we need to Find m(H2):

n(Na)(moles Na)= mass/Molar mass = 13g/23 g/mol = 0.57 mol.

According to equation mole ratio n(Na):n(H2)= 2:1,

then n(H2)=n(Na)/2

                =0.57/2=0.29 mol.

∴m(H2)= moles * molar mass

          =0.29 mol *2g/mol

          = 0.58 g

∴m solution= 247 g + 13 g – 0.58 g = 259.42 g

and when q=4.18 J/K g* 259.42 g *(339.7 K – 298 K)= 45218 J

The temperature of solution increased because heat was absorbed by the solution (q>0).

Then ΔHrxn= -q = -45218 J per 0.57 mol of Na

3- now we need to Find ΔHrxn per 1 mole of Na

ΔHrxn = -45218J/0.57 mol = -79331 J/mol ≈ -79 kJ/mol

ill try to . no promises tho.

explanation:

conduction is the transfer of thermal energy (heat in transfer) due to collisions between the molecules in the object. collisions between adjacent atoms and molecules transfer kinetic energy from the warmer to the cooler object. the objects must be in physical contact.