Calculations
A 200 g aqueous solution is 20% (by mass) NaCl (m.w. = 58.44 g mol–1). What is the mole fraction of NaCl?
0.072
A Br∅nsted-Lowry base is defined as a substance that ________.
A) increases [H+] when placed in H2O
B) decreases [H+] when placed in H2O
C) increases [OH-] when placed in H2O
D) acts as a proton acceptor
E) acts as a proton donor
D) acts as a proton acceptor
Which one of the following pairs cannot be mixed together to form a buffer solution?
A) HONH2, HONH3Cl
B) NaCl, HCl
C) RbOH, HF
D) KOH, HNO2
E) H2SO3, KHSO3
B) NaCl, HCl
Which of the following is released by the combustion of fossil fuels?
A) N2
B) CO2
C) H2
D) O2
E) O3
B) CO2
The primary detrimental effect of the presence of large amounts of biodegradable organic materials in water is ________.
A) it causes death of bottom dwelling organisms because it agglutinates and settles to the bottom, poisoning bottom dwelling organisms
B) it causes oxygen depletion in the water
C) it rises to the surface and absorbs wavelengths needed by aquatic plants
D) it decomposes endothermically causing the temperature of the water to decrease below the limits within which most aquatic organisms can live
E) it causes the water to become murky
B) it causes oxygen depletion in the water
Find the number of moles AND the molarity of a solution in which 0.850 grams of ammonium nitrate are dissolved in 345 mL of solution?
0.0106 mole NH4NO3
M=.0308M
A substance that is capable of acting as both an acid and as a base is ________.
A) autosomal
B) conjugated
C) amphiprotic
D) saturated
E) miscible
C) amphiprotic
The Henderson-Hasselbalch equation is ________.
A) [H+] = Ka + [base/acid]
B) pH = pKa - log [base/acid]
C) pH = pKa + log [base/acid]
D) pH = pKa + log [acid/base]
E) pH = log [acid/base]
C) pH = pKa + log [base/acid]
Of the reactions involved in the photodecomposition of ozone (shown below), which are exothermic?
1. O2 (g) + hν → O (g) + O (g)
2. O (g) + O2 (g) + M (g) → O3 (g) + M* (g)
3. O3 (g) + hν → O2 (g) + O (g)
4. O (g) + O (g) + M (g) → O2 (g) + M* (g)
A) 2 and 4
B) 1 and 3
C) 1, 2, and 4
D) 2 only
E) all of them
A) 2 and 4
Eutrophication of a lake is the process of ________.
A) rapid increase in the amount of dead and decaying plant matter in the lake as a result of excessive plant growth
B) rapid decline in the lake's pH due to acid rain
C) dissolved oxygen being depleted by an overpopulation of fish
D) stocking the lake with fish
E) restoration of the lake's dissolved oxygen supply by aerobic bacteria
A) rapid increase in the amount of dead and decaying plant matter in the lake as a result of excessive plant growth
6.80 g of sodium chloride are added to 2750 mL of water. Find the mole fraction of the SODIUM CHLORIDE AND of the WATER in the solution.
mole fraction NaCl=7.59 x 10-4
mole fraction H2O=0.999
The molar concentration of hydronium ion in pure water at 25 °C is ________.
A) 0.00
B) 1.0 × 10-7
C) 1.0 × 10-14
D) 1.00
E) 7.00
B) 1.0 × 10-7
The ________ and ________ are the principal organs that regulate the pH of the carbonic acid-bicarbonate buffer system in the blood.
A) kidneys, liver
B) lungs, skin
C) lungs, kidneys
D) brain stem, heart
E) spleen, liver
C) lungs, kidneys
15) The source(s) of sulfur dioxide in the atmosphere is/are ________.
A) volcanic gases
B) forest fires
C) bacterial action
D) fossil-fuel combustion
E) all of the above
E) all of the above
What compound in limestone and marble is attacked by acid rain?
A) hydroxyapatite
B) calcium carbonate
C) gypsum
D) graphite
E) potassium hydroxide
B) calcium carbonate
Given: pH = 6.77
Wanted: [H+]
1.70 × 10-7 M H+
Of the following acids, ________ is a strong acid.
A) HNO2
B) H2CO3
C) HNO3
D) HClO
E) HF
C) HNO3
Decreasing the pH of blood will cause hemoglobin to release ________.
A) CO2
B) N2
C) H2
D) O2
E) Fe
D) O2
What is meant by the salinity of seawater?
A) percent by mass of salt in seawater
B) mass in grams of dry salts present in 1 kg of seawater
C) molality of NaCl in seawater
D) osmotic pressure of seawater
E) molarity of NaCl in seawater
B) mass in grams of dry salts present in 1 kg of seawater
A 5 g aqueous solution is 20% (by mass) NaCl (m.w. = 58.44 g mol–1). What is the mole fraction of NaCl?
.072
Given: [H+] = 2.96 × 10-1 mol/L
Wanted: pOH?
13.5
Which one of the following is the weakest acid?
A) HF (Ka = 6.8 × 10-4)
B) HClO (Ka = 3.0 × 10-8)
C) HNO2 (Ka = 4.5 × 10-4)
D) HCN (Ka = 4.9 × 10-10)
E) Acetic acid (Ka = 1.8 × 10-5)
D) HCN (Ka = 4.9 × 10-10)
Why does fluoride treatment render teeth more resistant to decay?
A) Fluoride kills the bacteria in the mouth that make the acids that decay teeth.
B) Fluoride stimulates production of tooth enamel to replace that lost to decay.
C) Fluoride reduces saliva production, keeping teeth drier and thus reducing decay.
D) Fluoride converts hydroxyapatite to fluoroapatite that is less reactive with acids.
E) Fluoride dissolves plaque, reducing its decaying contact with teeth.
D) Fluoride converts hydroxyapatite to fluoroapatite that is less reactive with acids.
The concentration of Na in seawater is 0.470 M. How many grams of Na can be extracted from 10.0 kg of seawater if the recovery rate is 60.0%?
A) 0.470
B) 64.8
C) 4.70
D) 108
E) 43.2
B) 64.8
A 100 g aqueous solution is 20% (by mass) NaCl (m.w. = 58.44 g mol–1). What is the mole fraction of NaCl?
.072