Question

1. The weak acid, HX, is neutralized by sodium hydroxide as shown below:

HX(aq) + NaOH(aq) → NaCN(aq) + H₂O(l).

Suppose you carried out this reaction in a coffee cup calorimeter using 50.0 mL of 0.500 M HX and 50.0 mL of 0.500 M NaOH.

If the temperature of the calorimeter increases by 2.51 °C, what is the enthalpy of this neutralization reaction (in kJ/mol)?

Assume the density of the solution is 1.00g/mL and that the specific heat is 4.184 J/g °C

2. Colorless gas nitric oxide gas, NO, can react with oxygen to form the brown gas nitrogen dioxide, NO₂, as shown below:

2 NO(g) + O₂(g) → 2 NO₂(g).

Suppose you wanted to carry out this reaction in the laboratory.  You could filled one gas syringe with 100. mL of nitric oxide and another with 111. mL of oxygen gas.

When you connected the syringes and mixed the gases, the reaction mixture changes to a brown color indicating the the reaction had occurred. If the syringes were maintained at constant temperature and pressure, what would be the expected volume of the reaction mixture after the reaction?

QUESTION 1 The weak acid, HX, is neutralized by sodium hydroxide as shown below HX(aq)NaOH(aq) NaCN(aq) + H20(). Suppose you carried out this reaction in a coffee cup calorimeter using 50.0 mL of 0.500 M HX and 50.0 mL of 0.500 M NaOH If the temperature of the calorimeter increases by 2.51 °C, what is the enthalpy of this neutralization reaction (in kJ/mol)? Assume the density of the solution is 1.00g/mL and that the specific heat is 4.184 J/g °C Enter your value with the appropriate sign and value, but no units. QUESTION 2 Colorless gas nitric oxide gas, NO, can react with oxygen to form the brown gas nitrogen dioxide, NO2, as shown below: 2 NO(g)O2(g) -»2 NO2(g) Suppose you wanted to carry out this reaction in the laboratory. You could filled one gas syringe with 100. mL of nitric oxide and another with 111 mL of oxygen gas. When you connected the syringes and mixed the gases, the reaction mixture changes to a brown color indicating the the reaction had occurred. If the syringes were maintained at constant temperature and pressure, what would be the expected volume of the reaction mixture after the reaction? Hint 1: it is not simply 100+111 mL Hint 2: nitric oxide is the limiting reagent, which means the end result is a combination of the product gas and the leftover oxygen gas.

Answer 1

Ans 1

Molarity of HX = 0.500 mol/L

Volume of HX = 50 mL

Moles of HX = molarity x volume

= 0.500 mol/L x 50 mL x 1L/1000 mL

= 0.025 mol

Molarity of NaOH = 0.500 mol/L

Volume of NaOH = 50 mL

Moles of NaOH = molarity x volume

= 0.500 mol/L x 50 mL x 1L/1000 mL

= 0.025 mol

From the stoichiometry of the reaction

Moles of NaOH used = moles of HX used = 0.025 mol

Total volume of solution = 50 + 50 = 100 mL

Mass of solution = volume x density

= 100 mL x 1g/mL

= 100 g

Heat released by reaction Q = - mass x Cp x temperature change

= - 100 g x 4.184 J/g°C x 2.51 °C

= - 1050.184 J x 1kJ/1000 J

= - 1.05 kJ

Enthalpy of neutralization reaction = Q/(moles of limiting reactant)

= (-1.05 kJ) / (0.025 mol)

= - 42 kJ/mol