Question

Changes in state are called phase changes. A phase change is a change from one physical state (gas, liquid, or solid) to another. The amount of energy necessary to melt 1 mole of any solid is called its enthalpy of fusion. The amount of energy necessary to vaporize 1 g of any substance is called its enthalpy of vaporization. The enthalpy of fusion of solid sodium is 2.60 kJ/mol. Calculate the energy required to melt 43.6 g of solid sodium.

Answer 1

To calculate the energy required to melt 43.6 grams of solid sodium, one must convert the mass to moles and then use the enthalpy of fusion to find the total energy needed. The energy required is 4.9296 kJ.

Step-by-step explanation:

The question involves calculating the energy required to melt a certain amount of solid sodium based on its enthalpy of fusion. First, we need to find the number of moles of sodium in 43.6 grams. The molar mass of sodium (Na) is approximately 22.99 grams per mole, so the number of moles in 43.6 grams is 43.6 g ÷ 22.99 g/mol, which equals about 1.896 moles. The enthalpy of fusion for sodium is given as 2.60 kJ/mol. To find the total energy required, we multiply the number of moles by the enthalpy of fusion: 1.896 moles × 2.60 kJ/mol = 4.9296 kJ. Therefore, the energy required to melt 43.6 grams of solid sodium is 4.9296 kJ.

Answer 2

the energy required is Q = 4.9 kJ

Step-by-step explanation:

Since the energy required is

Q = L * n

where L = molar enthalpy of fusion of solid sodium = 2.60 kJ/mol

and n = number of moles involved

also we know that

n= m/ M , where m= mass involved , M = molecular weight of sodium

the molecular weight of sodium is M= 23 g / mol

therefore

Q = L * n = L* m / M

replacing values

Q = L* m / M = 2.60 kJ/mol * 43.6 g/ (23 g / mol) = 4.9 kJ

Q = 4.9 kJ

thus the energy required is Q = 4.9 kJ