Acid-Base
Are the following the same? H30+ and H+ (and what are their names)
yes, hydronium and hydrogen proton
What is the O.N. for Zn(s) and explain why?
0 because it is a pure element
How many mmHg are in 1 atm?
760 mmHg=1 atm
What is the pH of an acidic solution?
<7pH
Is the following an exothermic or endothermic reaction?
50.9 + CH4 (l) --> CH4 (g)
endothermic
Is an acid a proton (H+) donor or acceptor?
donor
What is the oxidizing agent?
the one that is reduced (gains e-)
What is the value for standard molar volume?
22.4 L (Volume of 1 mol ideal gas)
As pH does down, [H3O+] goes (up/down)?
up, [H3O+] increases in an acidic soln
If a piston is compressed, creating pressure on the system, having work done on it what is the sign of work (positive/negative)?
+w
Is HClO4 a strong acid and does it dissociate completely or not?
Yes, it is a strong acid that dissociates completely
Is the following a redox reaction? Explain.
NH3 (aq) + HCl (aq) → NH4Cl (aq)
No, nothing is oxidized or reduced because O.N. don’t change.
-3 +1 +1 -1 -3 +1 -1
NH3 (aq) + HCl (aq) → NH4Cl (aq)
When we are calculating using gas laws do we use Kelvin or Celsius to determine temperature?
Kelvin (need R value to cancel)
Because the concentrations of [H3O+] and [OH-] are numbers that are SUPER small, what does pH or pOH equal to in the pH/pOH scale?
pH=-log[H3O+] pOH=-log[OH-]
Heat (q)
Work (w)
Are weak acids considered electrolytes?
Yes, they would be weak electrolytes. The are simply "dimmer"--conduct electricity less well
Should the number of e- gained and the number lost equal each other?
yes, this is why we have to balance electrons in redox half reactions
What are the STP units for the following:
Pressure (in atm and torr)
Temperature (in degrees C and K)
P=1atm=760torr
t=0C=273K
What are the 4 equations you need to memorize for pH problems?
pH=-log[H3O+] [H3O+]=10-pH
pOH=-log[OH-] [OH-]=10-pOH
If a piston expands, where the work is done by the system what is the sign of work (positive/negative)?
-w, releasing energy as work
Group the following on the board into Strong Acids vs Weak Acids:
HF, CH3COOH, H2SO4, H3PO4, HCl
WEAK:
HF, CH3COOH (Carboxylic acids are weak), H3PO4
STRONG:
H2SO4, HCl
What do oxidation numbers represent? How are they different from charges?
Oxidation numbers represent electrons lost or gained and are assigned to each individual atom. Charges are different because they are assigned to a whole compound or ion.
Convert 267 degrees K to C
267-273= -6C
What does Kw represent?
Ion-product equalibrium constant for water, Kw=[H3O+][OH−]. At 25 °C, Kw is 1.01×10−14
If an enthalpy diagram's Hi is below Hf, is this an exothermic or endothermic reaction?
endothermic, heat absorbed