Question

When 0.201 g of sodium metal is added to an excess of hydrochloride acid, 2090 J of heat are produced. What is the enthalpy of the reaction as written? 2Na(s) + 2HCI(aq) + H2(g)Enthalpy of reaction = ___________ kJ

Answer 1

-239.13kJ/mol

Explanations:

The complete chemical reaction between the sodium metal and hydrochloric acid is expressed as shown:

`2Na(s)+2\text{HCl(aq)}\rightarrow2NaCl(aq)+H_2(g)`

The enthalpy of the reaction is expressed using the formula;

`\triangle H^0_(rxn)=\frac{Quantity\text{ of h}eat}{Moles\text{ of sodium}}`

Given that quantity of energy released is -2090J (Since energy is released by the system)

Get the moles of sodium

`\begin{gathered} Moles\text{ of sodium =}\frac{Mass\text{ of Na}}{Molar\text{ mass of Na}} \\ \text{Moles of sodium =}\frac{0.201g}{22.99\text{g/mol}} \\ \text{Moles of sodium = }0.00874\text{moles of Na} \end{gathered}`

Next is to get the required enthalpy of the reaction in kJ/mol

`\begin{gathered} \text{Enthalpy of the reaction = }\frac{-2.090kJ}{0.00874\text{mol}} \\ \text{Enthalpy of the reaction = -}239.13\text{kJ/mol} \end{gathered}`

Hence the enthalpy of the reaction is -239.13kJ/mol