Heat of precipitation

A chemical reaction that absorbs heat from the surroundings is said to be __________ and has a __________ ΔH at constant pressure.

• endothermic; positive
• endothermic; negative
• exothermic; negative
• exothermic; positive

Tags

NGSS.HS-PS1-4

Convert 42 kJ into joules

• 0.042 J

• 4200 J

• 42000 J

• 420 J

What is the formula for calculating heat?

• H = mc $\theta$

• H = ΔH x n

• H = ΔH x mass

• products - reactants

Which of the following pairs of solutions has the same heat of precipitation as the reaction between lead (II) nitrate and hydrochloric acid?

• Barium chloride and sodium sulphate

• Calcium chloride and sodium carbonate

• ammonium chloride and silver nitrate

• copper (II) chloride and lead (II) nitrate

What is precipitation reaction?

• Two different aqueous soluble salts are mixed to form a soluble salt.

• Two different aqueous soluble salts are mixed to form an insoluble salt.

• Two different aqueous soluble salts are mixed to form an insoluble salt and a soluble salt.

• One aqueous soluble salts are mixed with one insoluble salt to form an insoluble salt.

The following equation shows the reaction between  $Ag^+$  and  $Cl^-$  ions.
 $Ag^+$  +  $Cl^-$  -> AgCl    $\Delta$ H= -65 $kJmol^{-1}$  
Which of the following is true about the above equation?

• Exothermic reaction occurs

• Heat is absorbed from the surrounding

• The energy content of the reactants is less than the products

• 65 kJ of heat is absorbed when 1 mole of silver chloride is formed

Why is a polystyrene cup used in the experiment to determine the heat of reaction involving two aqueous solution?

• To allow the temperature of the reaction to increase uniformly

• So that the reaction takes place completely

• To reduce the heat loss to the surrounding

• To increase the quantity of heat loss to the surrounding

Ionic equation for precipitation of silver chloride is shown below:
 $Ag^+$  +  $Cl^-$  -->  AgCl
Which of the following statement is correct when defining heat of precipitation based on the chemical reaction.

• Heat of precipitation is the heat change when 1 mol of precipitate is form from its ions.

• Heat of precipitation is the heat change when precipitate is form from its ions.

• Heat of precipitation is the heat change when 1 mol of silver chloride is form from silver ion and chloride ion.

• Heat of precipitation is the heat change when silver chloride is form from silver ion and chloride ion.

When $AgNO_3$ reacts with NaCl solution, the temperature changed by x  $\degree$  C. Which of the following solution is suitable to be use to replace NaCl and will give the same amount of temperature change?

• lead (II) nitrate

• lead (II) chloride

• Potassium chloride

• Potassium nitrate

The thermochemical equation for precipitation of lead (II) sulphate is as follows: $Pb^{2+}+SO_{4\ ^{ }}^{2-}\ \ ->\ \ PbSO_4$   $\Delta H\ =\ -65.5\ kJmol^{-1}$  
Calculate the temperature change when  $100cm^3\ of\ 0.5moldm^{-3}$  lead (II) nitrate solution is added to  $100\ cm^{3^{ }}of\ 0.5\ moldm^{-3}$  potassium sulphate solution

• 2.8  $\degree C$  

• 3.9  $\degree C$  

• 4.2  $\degree C$  

• 1.9  $\degree C$