Unit 4 Chem Retake

If sulfur dioxide and oxygen can be made into sulfur trioxide, what is the reverse reaction?

• SO3+O2-->SO5

• SO2+2SO3-->3S+4O2

• 2SO2-->2SO2+O2

• 2SO2+O2-->2SO3

An 8.0g sample of magnesium and an 80mL sample of silver nitrate are used in a chemical reaction.

Which combination of these samples has the fastest reaction rate?

• A magnesium strip and 3.0M AgNO3

• A magnesium strip and 1.0M AgNO3

• Magnesium granules and 3.0M AgNO3

• Magnesium granules and 1.0M AgNO3

What happens to a reaction at equilibrium when more reactant is added to the system?

• The reaction makes more products

• The reaction is unchanged

• The reaction makes more reactants

• The answer can not be determined

Which of the changes listed below would shift the following reaction to the right?

4HCl(g)+O2(g)-->2Cl2(g)+2H2O(g)

• Decrease the pressure

• Addition of Cl2

• Increase the pressure

• Removal of O2

Which expression correctly describes activation energy in a chemical reaction?

• energy given off when reactants collide

• heat released during reaction

• total amount of energy consumed by the reaction

• energy barrier between reactants and products

Why does a catalyst cause a reaction to proceed faster?

• increases the total energy of collisions

• decreases the need for an activated completx

• decreases the activation energy of a reaction

• increases the frequency of collisions

What is the effect of adding more water to the following equilibrium reaction?

CO2+H2O<-->H2CO3

• There is no effect

• CO2 concentration increases

• The equilibrium is pushed in the direction of the reactants

• More H2CO3 is produced

Consider the reaction N2(g)+3H2(g)<-->2NH3(g) What is the effect of decreasing the volume on the contained gases?

• The system reacts by increasing the number of gas molecules

• Ammonia is consumed in the reaction

• The reaction shifts toward the product gas

• The pressure on the gases decreases momentarily

Why does a higher temp. cause a reaction to go faster?

• Collisions occur more frequently and they occur w/ greater energy

• Collisions are not as frequent but each collision has more energy

• Collisions between molecules occur more slowly so there's more time to react

• Collisions have less energy so molecules are less likely to bounce away from one another

Consider the following equilibrium: H2(g)+I2(g)<-->2HI(g) △H=-40kJ/mol

Which change will shift this to the left?

• increase temp.

• adding catalyst

• reducing volume

• adding H2

• removing some HI