Answer:
1
The reaction is exothermic
2
[tex]H = -1.1 \ KJ[/tex]
3
[tex]\Delta H_{rxn} = -6.24 \ KJ/ mol[/tex]
Explanation:
From the question we are told that
The mass of the sodium chloride is (NaCl ) is [tex]m_s = 10.3 \ g[/tex]
The mass of water is [tex]m_w = 250 \ g[/tex]
The initial temperature is [tex]T_i = 23^oC[/tex]
The temperature after 3 minutes is [tex]T_3 = 22.2 ^oC[/tex]
The time taken for temperature to fall is t = 3 minutes
The reaction is
[tex]NaCl_{ (s)} \rightarrow Na^+ _{(aq)} + Cl^-_{ (aq)}[/tex]
The reaction is exothermic because the temperature fell
Generally the mass of the solution is mathematically represented as
[tex]M = m_w + m_s[/tex]
=> [tex]M = 250 + 10.3 [/tex]
=> [tex]M = 260.3 \ g [/tex]
Gnerally the heat energy released from the solution is mathematically represented as
[tex]H = M * C_s * (T_3 - T_i)[/tex]
Here [tex]C_s[/tex] is the specific heat of solution which for this question we would assume it is the specific heat of water which has a value of
[tex]Cs = C_w = 4.18 J/g^oC[/tex]
So
[tex]H = 260.3 * 4.18 * (22- 23)[/tex]
[tex]H = -1088.054 \ J[/tex]
[tex]H = -1.088054 \ KJ[/tex]
[tex]H = -1.1 \ KJ[/tex]
Generally the number of moles of NaCl is mathematically represented as
[tex]nNaCl = \frac{m_s}{zNaCl}[/tex]
Here [tex]zNaCl[/tex] is the molar mass of NaCl and the value is
[tex]zNaCl = 58.44 \ g/mol[/tex]
So
[tex]nNaCl = \frac{10.3}{58.44 }[/tex]
=> [tex]nNaCl = 0.1762 \ moles[/tex]
Generally reaction enthalpy is mathematically represented as
[tex]\Delta H_{rxn} = \frac{H}{nNaCl}[/tex]
[tex]\Delta H_{rxn} = \frac{-1.1}{0.1762 }[/tex]
[tex]\Delta H_{rxn} = -6.24 \ KJ/ mol[/tex]
