fuels and heats of reaction experiments - To determine the heat of reaction between HCI and NaOH

2018

The cardboard cup with plastic lid in the diagram contained 150 cm} of 1.0 M hydrochloric acid solution at room temperature. A volume of 160 cm} of 1.0 M sodium hydroxide solution - also at room temperature - was added quickly and the mixture was stirred. The temperature of the mixture rose rapidly by 6.4 K and then began to fall gradually.

The equation for the neutralisation reaction that took place is:

HCI + NaOH -> NaCl + H2O

(a) Is this reaction exothermic or endothermic? Justify your answer.

Exothermic

temperature goes up / heat given out

2018

The cardboard cup with plastic lid in the diagram contained 150 cm} of 1.0 M hydrochloric acid solution at room temperature. A volume of 160 cm} of 1.0 M sodium hydroxide solution - also at room temperature - was added quickly and the mixture was stirred. The temperature of the mixture rose rapidly by 6.4 K and then began to fall gradually.

The equation for the neutralisation reaction that took place is:

HCI + NaOH -> NaCl + H2O

(a) Why should the mixture be stirred beforg, taking temperature readings?

distribute heat evenly / avoid taking temperature of a hot (cold) spot (place) / get a more accurate result / ensure complete (fast) reaction

2018

The cardboard cup with plastic lid in the diagram contained 150 cm} of 1.0 M hydrochloric acid solution at room temperature. A volume of 160 cm} of 1.0 M sodium hydroxide solution - also at room temperature - was added quickly and the mixture was stirred. The temperature of the mixture rose rapidly by 6.4 K and then began to fall gradually.

The equation for the neutralisation reaction that took place is:

HCI + NaOH -> NaCl + H2O

Suggest a reason why the temperature, having risen,then began to fall gradually.

heat loss to the surroundings / cardboard is not a good insulator / the solution is hotter than the room (surroundings

2018

The cardboard cup with plastic lid in the diagram contained 150 cm} of 1.0 M hydrochloric acid solution at room temperature. A volume of 160 cm} of 1.0 M sodium hydroxide solution - also at room temperature - was added quickly and the mixture was stirred. The temperature of the mixture rose rapidly by 6.4 K and then began to fall gradually.

The equation for the neutralisation reaction that took place is:

HCI + NaOH -> NaCl + H2O

(i) The thermometer used was accurate to 0.1 K. What temperature rise would have been recorded if the thermometer used was accurate to 1 K?

6 K

2018

The cardboard cup with plastic lid in the diagram contained 150 cm} of 1.0 M hydrochloric acid solution at room temperature. A volume of 160 cm} of 1.0 M sodium hydroxide solution - also at room temperature - was added quickly and the mixture was stirred. The temperature of the mixture rose rapidly by 6.4 K and then began to fall gradually.

The equation for the neutralisation reaction that took place is:

HCI + NaOH -> NaCl + H2O

(i) Why is it advantageous to use moderately concentrated solutions instead of dilute solutions in this experiment?

bigger temperature rise recorded / giving more accurate result / as a result AH more accurate / less percentage error / temperature rise easier to measure accurately

2018

The cardboard cup with plastic lid in the diagram contained 150 cm} of 1.0 M hydrochloric acid solution at room temperature. A volume of 160 cm} of 1.0 M sodium hydroxide solution - also at room temperature - was added quickly and the mixture was stirred. The temperature of the mixture rose rapidly by 6.4 K and then began to fall gradually.

The equation for the neutralisation reaction that took place is:

HCI + NaOH -> NaCl + H2O

(a) The result obtained in this experiment was about 3% below the expected value. State and explain a modification to the method described that would give a more accurate result.

STATE 1

Use more insulation/wrapped in cotton wall

2018

The cardboard cup with plastic lid in the diagram contained 150 cm} of 1.0 M hydrochloric acid solution at room temperature. A volume of 160 cm} of 1.0 M sodium hydroxide solution - also at room temperature - was added quickly and the mixture was stirred. The temperature of the mixture rose rapidly by 6.4 K and then began to fall gradually.

The equation for the neutralisation reaction that took place is:

HCI + NaOH -> NaCl + H2O

(a) The result obtained in this experiment was about 3% below the expected value. State and explain a modification to the method described that would give a more accurate result.

STATE 1

Use more insulation/wrapped in cotton wall

EXPLAIN

Gives more accurate temperature rise (change)/stops (reduces) heat loss to surroundings/more accurate result for heat produced in cup

2018

The cardboard cup with plastic lid in the diagram contained 150 cm} of 1.0 M hydrochloric acid solution at room temperature. A volume of 160 cm} of 1.0 M sodium hydroxide solution - also at room temperature - was added quickly and the mixture was stirred. The temperature of the mixture rose rapidly by 6.4 K and then began to fall gradually.

The equation for the neutralisation reaction that took place is:

HCI + NaOH -> NaCl + H2O

(a) The result obtained in this experiment was about 3% below the expected value. State and explain a modification to the method described that would give a more accurate result.

STATE 2

Use polystyrene (plastic) cup

2018

The cardboard cup with plastic lid in the diagram contained 150 cm} of 1.0 M hydrochloric acid solution at room temperature. A volume of 160 cm} of 1.0 M sodium hydroxide solution - also at room temperature - was added quickly and the mixture was stirred. The temperature of the mixture rose rapidly by 6.4 K and then began to fall gradually.

The equation for the neutralisation reaction that took place is:

HCI + NaOH -> NaCl + H2O

(a) The result obtained in this experiment was about 3% below the expected value. State and explain a modification to the method described that would give a more accurate result.

STATE 2

Use polystyrene (plastic) cup

EXPLAIN

Gives more accurate temperature rise change/stops reduce heat loss to surroundings/more accurate results for heat produced in cup/better insulation than cardboard

2013

A reaction vessel of negligible heat capacity held 75 cm' of 1.0 M HI solution at a temperature of 13.0°C. A thermometer was placed in the liquid in the reaction vessel. A graduated cylinder was used to measure out and add 75 cm' of 1.0 M NaH solution at a temperature of 15.0 °C to the reaction vessel. The highest temperature of the reaction mixture was recorded as 20.9 °C. This information was used to calculate the heat of reaction of hydrochloric acid with sodium hydroxide.

The equation for the reaction is:

HCL + NaOH -> NaCL + H2O

A) Define heat of reaction.

heat change when the numbers of moles of reactants in the balanced equation react completely / heat change for reaction according to balanced equation

2013

A reaction vessel of negligible heat capacity held 75 cm' of 1.0 M HI solution at a temperature of 13.0°C. A thermometer was placed in the liquid in the reaction vessel. A graduated cylinder was used to measure out and add 75 cm' of 1.0 M NaH solution at a temperature of 15.0 °C to the reaction vessel. The highest temperature of the reaction mixture was recorded as 20.9 °C. This information was used to calculate the heat of reaction of hydrochloric acid with sodium hydroxide.

The equation for the reaction is:

HCL + NaOH -> NaCL + H2O

B) Suggest a suitable material for the reaction vessel to avoid heat loss to the surroundings.

polystyrene / plastic /styrofoam / paper / cardboard / other named good insulating material

2013

A reaction vessel of negligible heat capacity held 75 cm' of 1.0 M HI solution at a temperature of 13.0°C. A thermometer was placed in the liquid in the reaction vessel. A graduated cylinder was used to measure out and add 75 cm' of 1.0 M NaH solution at a temperature of 15.0 °C to the reaction vessel. The highest temperature of the reaction mixture was recorded as 20.9 °C. This information was used to calculate the heat of reaction of hydrochloric acid with sodium hydroxide.

The equation for the reaction is:

HCL + NaOH -> NaCL + H2O

C) State (1) one advantage of the use of a burette instead of a graduated cylinder for measuring out the base and adding it to the reaction vessel.

more accurate (accuracy) / delivers the measured volume (doesn't

leave part of the measured volume behind on sides) //

2013

A reaction vessel of negligible heat capacity held 75 cm' of 1.0 M HI solution at a temperature of 13.0°C. A thermometer was placed in the liquid in the reaction vessel. A graduated cylinder was used to measure out and add 75 cm' of 1.0 M NaH solution at a temperature of 15.0 °C to the reaction vessel. The highest temperature of the reaction mixture was recorded as 20.9 °C. This information was used to calculate the heat of reaction of hydrochloric acid with sodium hydroxide.

The equation for the reaction is:

HCL + NaOH -> NaCL + H2O

C) State (ii) one disadvantage, of the use of a burette instead of a graduated cylinder for measuring out the base and adding it to the reaction vessel.

slow addition / two 50 cm' burettes needed (burette to measure 75 cm3

usually not available in school laboratory) / difficult to measure 75 cm3

2013

A reaction vessel of negligible heat capacity held 75 cm' of 1.0 M HI solution at a temperature of 13.0°C. A thermometer was placed in the liquid in the reaction vessel. A graduated cylinder was used to measure out and add 75 cm' of 1.0 M NaH solution at a temperature of 15.0 °C to the reaction vessel. The highest temperature of the reaction mixture was recorded as 20.9 °C. This information was used to calculate the heat of reaction of hydrochloric acid with sodium hydroxide.

The equation for the reaction is:

HCL + NaOH -> NaCL + H2O

D) State two ways of ensuring that the rise in temperature was measured as accurately as possible

sensitive (precise, accurate, reading to 0.2°C or better (not "digital" alone) thermometer (or else a temperature sensor or temperature probe) // add quickly // avoid splashing // cover quickly (immediately) // stir (mix) // after addition plot temperature at intervals and get highest temperature by extrapolating back to time of mixing

2013

A reaction vessel of negligible heat capacity held 75 cm' of 1.0 M HI solution at a temperature of 13.0°C. A thermometer was placed in the liquid in the reaction vessel. A graduated cylinder was used to measure out and add 75 cm' of 1.0 M NaH solution at a temperature of 15.0 °C to the reaction vessel. The highest temperature of the reaction mixture was recorded as 20.9 °C. This information was used to calculate the heat of reaction of hydrochloric acid with sodium hydroxide.

The equation for the reaction is:

HCL + NaOH -> NaCL + H2O

The solutions used in this experiment were moderately concentrated.

Identify the hazard associated with the use of these solutions.

Corrosive

2013

A reaction vessel of negligible heat capacity held 75 cm' of 1.0 M HI solution at a temperature of 13.0°C. A thermometer was placed in the liquid in the reaction vessel. A graduated cylinder was used to measure out and add 75 cm' of 1.0 M NaH solution at a temperature of 15.0 °C to the reaction vessel. The highest temperature of the reaction mixture was recorded as 20.9 °C. This information was used to calculate the heat of reaction of hydrochloric acid with sodium hydroxide.

The equation for the reaction is:

HCL + NaOH -> NaCL + H2O

What experimental problem would have been encountered if 0.1 M NaOH and 0.1 M HCI

solutions had been used instead of 1.0 M solutions?

very small temperature rise (change) / small heat change / hard to measure temperature

rise (heat change) accurately / greater percentage error