Solutions
A solution at 25 C contains 8721 mL of water and 394.6 g of solute. What is the correct % w/w concentration? The density of water is 1 g/mL.
4.329%
What is the conjugate base of bicarbonate (HCO3-)?
CO32-
The activation energies characteristics of the reversible chemical reaction A+B ⇌ C are Eforward = 53 kJ/mol and Eback=82 kJ/mol. Calculate the heat of the reaction. Is it exothermic or endothermic?
ΔHrxn=-29 kJ/mol. The forward reaction is exothermic.
In your backyard you collect water from a pond and determine that the pH is 3.88. What is the concentration of the hydroxide ions present?
7.6 x 10-11 M
What would be the effect on the activation energy by adding a catalyst to a reaction?
Ea would be reduced.
How many grams of nitrite are contained in 976.0 mL of a 57.9% w/v aqueous nitrite solution?
5.65 x 102 g
The Ka for a weak acid is 3.84 x 10-5. What is the pKa of its corresponding conjugate base?
9.584
Given the reaction NO2(g)+CO(g)-->NO(g)+CO2(g), calculate the reaction rate if the two reactants are mixed, and after 5.13 minutes, the concentration of CO2 is 0.525 mol/L.
Hint: units are mol per liter per second
1.71 x 10-3 mol per liter per second
How many grams of maltose (C12H22O11) would you have to add to 145.3 mL of water to obtain a 1.72 M concentration of maltose? (Molecular weight of maltose is 342.3 g/mol)
85.5 g
Recall an endothermic equilibrium reaction diagram. Which of the following best describes the ΔHrxn?
A. The difference in energy between A & B.
B. The difference in energy between A+B and X (transition state).
C. The difference in energy between C & D.
D. The difference in energy between C+D and A+B.
D. The difference in energy between C+D and A+B.
Based on the solubility rules, which statement about solubility is correct?
A. All nitrate salts are insoluble.
B. Calcium phosphate is soluble.
C. Group I carbonate salts are insoluble.
D. Ammonium sulfide salts are soluble.
D. Ammonium sulfide salts are soluble.
Calculate the pH of an aqueous solution consisting of 0.0080 M acetic acid and 0.0060 M sodium acetate.
Hint: pKa of acetic acid is 4.76
4.63
Which statement is true about the reaction: 44.76 kJ + A + B ⇌ C + D?
a. The forward and reverse reactions are exothermic.
b. The forward rxn is exothermic, reverse can be either endothermic or exothermic.
c. The forward rxn is exothermic, reverse is endothermic.
d. The forward reaction is endothermic, reverse is exothermic.
d. The forward reaction is endothermic, reverse is exothermic.
Calculate the hydroxide ion concentration in an aqueous 0.00200 M HCl solution.
5.00 x 10-12 M
T/F? A volume of a substance of known concentration is split into four different volumes. The concentration of the resulting solutions directly depends on the particular volumes of each of the differently divided solutions.
False. Concentration remains the same.
What is the final volume of a 0.0015 M solution prepared by dilution of 100 mL of a 0.090 M solution?
6.0 L
What is the correct pH of a solution that consists of 0.359 M lactic acid (HC3H5O3) and 0.972 M sodium lactate (NaC3H5O3)? The Ka of lactic acid is 1.387 x 10-4.
4.290
How would equilibrium be affected, in terms of amount of products, if heat is added to an endothermic reaction?
More products would be present at equilibrium.
How would you prepare 1.00 L of a 0.650 M aqueous solution of CaCl2 and how many grams of CaCl2 would be required?
Weigh out the 72.2 g of CaCl2 and dissolve it in sufficient water to make 1.00 L of solution.
What is the difference between osmotic pressure and hydrostatic pressure?
Osmotic pressure is the pressure generated by a difference in concentration of dissolved substances separated by a semipermeable membrane. Hydrostatic pressure is the pressure generated within a liquid by mechanical means.
Creatine is produced as a result of muscle metabolism. Normal creatine concentrations in blood are sometimes reported as 1.5 mg%. Calculate the concentration of blood creatine in units of mg per mL.
Hint: mg% = mg of solute / 100 mL of solution x 100
0.015 mg/mL
Pb(NO3)2(aq)+2KI(aq)→2KNO3(aq)+PbI2(s). Keq for the reaction is 6.29 x 10-5. The number of moles at equilibrium (in 1L) for Pb(NO3)2=1.36 mole, KI=1.23 mole, KNO3=?, PbI2=1.52 mole. What is the equilibrium concentration of KNO3?
1.14 x 10-2 M
Describe Le Chatelier's principle.
If a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change.
Titration: Which of the following was the correct molar concentration of 52.6 mL of an aqueous solution of chromic acid (H2CrO4) solution that required 0.813 L of a 0.0440 M standard solution of KOH for complete neutralization?
3.40 x 10-1 M
Hypotonic conditions: rate of water ____ the cell is greater than the rate of water _____. What is the result of these conditions?
Hypertonic conditions: rate of water ____ the cell is greater than the rate of water _____. What is the result of these conditions?
Isotonic conditions: the rates of water entering and leaving are _____. What is the result of these conditions?
Hypotonic conditions: rate of water entering the cell is greater than the rate of water leaving. Result: swelling or possible bursting.
Hypertonic conditions: rate of water leaving the cell is greater than the rate of water entering. Result: shrinkage.
Isotonic conditions: same rates. Result: no change in volume or shape.