Gen Chem II Exam III

buffers

100

T/F: A buffer changes the pH slightly, thus we want a small concentration of the buffer

False

200

Name a potential buffer

any weak acid conjugate pair

300

Calculate the pH of a buffer with .50 H₂S and .50 HS^-, the Pka is 4.7.  

4.7 

400

What creates a higher buffer capacity? 

high concentration of buffer components 

500

T/F: buffers have a usable range within +/- 3 pH units of the Pka of the acid component 

false 

Acidity

100

the dissociation of an acid is influenced by two factors: 

bond strength 

bond polarity 

200

What is likely pH of buffer between these option: 1.6 x 10 ^-5, 1.6 x 10 ^-7 , or 1.6 x 10 ^-9

1.6 x 10 ^-9

300

what is the relationship between bond strength and acid strength 

greater the bond strength, weaker the acid (HF) 

400

For oxoacids with the same central element but different # of oxygen atoms--how do we determine acid strength? 

number of O atoms 

500

The salt NaCl was formed. The cation of the strong base yields what type of solution? 

neutral 

thermochemistry

100

A spontaneous reaction often has what type of heat change, but not always true

exothermic 

200

For a spontaneous endothermic the particles have more/less freedom of motion? 

more freedom

300

When the surroundings must continuously supply energy for a change to occur, we call this..

nonspontaneous 

400

How can we predict the direction of spontaneity? 

comparing Q and K 

500

What is temperature's relationship with entropy?  

T increases, disorder increases 

solubility

100

the equilibrium constant for slightly soluble ionic compounds in water

Ksp

200

What is the Ksp expression for MgCO_{3 (s)}

[Mg ²⁺][CO₃ ^2-]

300

What is the Ksp expression K₂O in water? 

[K⁺]²[OH^-]²

400

If Q is less than K...what type of preciptate will form? 

none, the solution is unsaturated and no precipitate will form 

500

Consider the reaction:Co(NO₃)_{2, we add some Iron nitrate to the solution, in which direction will the rxn proceed?}

to the left

acids/bases equilibria

100

a substance with a proton donor is called

acid 

200

As the concentration of [H⁺] increases, pH...

decreases 

300

Ammonia has a pH of 11.5, calculate the [H⁺]. 

3.16 x 10 ^-12

400

We have two bases. Base X Pka of 9 and base Y has  a Kb of 1.6 x 10 ^-9. _{which is more acidic?} 

base Y 

500

Chemists are looking at the dissociation of H₃PO₄ and its ionizable protons. They notice that the difficulty of dissociation decreases between each proton dissociation and the Ka value is larger. 

T/F:  

False.