Chemistry Regent - June 2016 Q11-20

A 10.0-gram sample of nitrogen is at STP. Which property will increase when the sample is cooled to 72 K at standard pressure?

• mass
• volume
• density
• temperature

Which element is a gas at STP?

• sulfur
• xenon
• potassium
• phosphorus

A 5.0-gram sample of Fe(s) is to be placed in 100. milliliters of HCl(aq). Which changes will result in the fastest rate of reaction? 

• increasing the surface area of Fe(s) and increasing the concentration of HCl(aq) 
• increasing the surface area of Fe(s) and decreasing the concentration of HCl(aq)
• decreasing the surface area of Fe(s) and increasing the concentration of HCl(aq) 
• decreasing the surface area of Fe(s) and decreasing the concentration of HCl(aq)

Which process is commonly used to separate a mixture of ethanol and water?

• distillation
• ionization
• filtration
• titration

A sample of hydrogen gas will behave most like an ideal gas under the conditions of 

• low pressure and low temperature 
• low pressure and high temperature 
• high pressure and low temperature 
• high pressure and high temperature

The collision theory states that a reaction is most likely to occur when the reactant particles collide with the proper 

• formula masses
• molecular masses
• density and volume 
• energy and orientation

At STP, which sample contains the same number of molecules as 3.0 liters of H₂(g)? 

• 1.5 L of NH₃(g) 
• 2.0 L of CO₂(g) 
• 3.0 L of CH₄(g)
• 6.0 L of N₂(g)

The addition of a catalyst to a chemical reaction provides an alternate pathway that 

• increases the potential energy of reactants
• decreases the potential energy of reactants
• increases the activation energy 
• decreases the activation energy

 A sample of water is boiling as heat is added at a constant rate. Which statement describes the potential energy and the average kinetic energy of the water molecules in this sample? 

• The potential energy decreases and the average kinetic energy remains the same.
• The potential energy decreases and the average kinetic energy increases.
• The potential energy increases and the average kinetic energy remains the same.
• The potential energy increases and the average kinetic energy increases. 

Entropy is a measure of the 

• acidity of a sample
• disorder of a system
• concentration of a solution
• chemical activity of an element