thermodynamics

One way to express the concentration of a solution is molarity. What does a molar salt solution contain?

• 1 mole of salt in 1 kg of water

• 1 mole of salt in 1 L of solution

• 1 mole of salt in 1 L of water

• 1 mole of salt in 1 mole of water

  A liter of salt solution containing 2 moles NaCl is 2 M in concentration. What is the molar concentration of a 5-liter salt solution containing 10 moles of NaCl?

• 3 mol/l or 3 M

• 4 mol/l or 4 M

• 2 mol/l or 2 M

• 7 mol/l or 7 M

  Dimercaprol is a compound used as an antidote for mercury or arsenic poisoning. This is prepared by mixing 100 mg of dimercaprol with 700 mg of peanut oil. What is the percent by mass of dimercaprol in this solution?

• 12.0%

• 12.1%

• 12.3%

• 12.5%

  Saccharin, one of the first non-nutritive sweeteners used in soft drinks, is 500 times sweeter that sugar in dilute aqueous solutions.  The solubility of saccharin is 100 g per 290 ml of solution.  What is the molarity of a saturated saccharin solution?

Molar mass of saccharin = 183.2 g/mol

• 0.0188 M

• 0.632 M

• 1.58 M

• 3.45 M

What volume of concentrated (14.7 M) phosphoric acid is needed to prepare 25.0 liters of 3.0 M H₃PO₄?

• 0.20 liter

• 0.57 liter

• 1.8 liters

• 5.1 liters

A reaction takes place endothermically. Which of the following statements best describes endothermic reactions?

• The temperature of the system drops

• The temperature of the surrounding drops

• The temperature of the surrounding rises

• The temperature of the surroundings remains the same

The heat of solution of NH₄NO₃ is +26.2 kJ/mol.  What change in heat will take place when a solution of NH₄NO₃ is diluted by addition of more water?

 

• Absorbed

• Evolved

• Released

• Unchanged

   Which of the following changes is exothermic?

• Frying of fish

• Melting of lard

• Drying of clothes

• Burning of gasoline

Since internal energy, pressure and volume are all state functions, enthalpy is also a state function. So we can define a change in enthalpy as ______

•  ΔH = Hfinal – Hinitial

•  ΔH = Hfinal + Hinitial

• ΔH = Hinitial – Hfinal

• ΔH = Hinitial + Hfinal

When the heat (q) involved in a particular process is assigned as (+), this means that…

• The process is spontaneous

• The process is exothermic

• The process involves the release of heat

• The process involves the absorption of heat