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Question
The time needed for a radioactive sample to decay to one-half of its original activity is called the ________.Answer
This answer is hidden. It contains 9 characters.
Related questions
Q:
Identify the Brnsted-Lowry acids in the following reaction.H2O + CO32- ->HCO3- + OH-A) H2O/HCO3-B) CO32-/HCO3-C) OH-/HCO3-D) CO32-/OH-E) H2CO3/H2O
Q:
According to the Brnsted-Lowry definition,
A) an acid is a proton acceptor.
B) a base produces H+ ions in aqueous solutions.
C) a base is a proton donor.
D) a base is a proton acceptor.
E) an acid acts as the solvent.
Q:
A catalyst lowers the activation energy of a chemical reaction.
Q:
For the following reaction, the equilibrium constant Kc is 2.0 at a certain temperature. Bromine can be liquefied easily and removed from the reaction vessel as it is formed. If this is done, how will it affect the equilibrium reaction?2NOBr(g) -> 2NO(g) + Br2(g)A) More products will be made as Br2 is removed.B) There will be a larger proportion NOBr in the vessel when equilibrium is reached.C) Less NO will be made.D) The pressure in the vessel will increase.E) The equilibrium constant will change.
Q:
In an exothermic reaction, heat can be considered a
A) reactant.
B) product.
C) rate.
D) catalyst.
E) determinant.
Q:
In the reaction of nitrogen gas with oxygen gas to produce nitrogen oxide, what is the effect of adding more oxygen gas to the initial reaction mixture? The reaction is shown below.N2(g) + O2(g) -> 2NO(g)A) The equilibrium shifts to produce more N2.B) The equilibrium shifts to produce more NO.C) The equilibrium is not affected.D) Extra catalyst is required to reach equilibrium.E) The temperature of the reaction mixture is raised.
Q:
The physiological equilibrium system that keeps the temperature of the body constant is called
A) stimulation.
B) regulation.
C) metabolism.
D) homeostasis.
E) catalysis.
Q:
When a reaction is at equilibrium,
A) all reaction stops.
B) no more reactants are converted to products.
C) the reaction is no longer reversible.
D) the forward and reverse reactions occur at the same rate.
E) the products and reactants have the same energy content.
Q:
A chemical reaction has reached equilibrium when
A) the concentrations of reactants and products are equal.
B) all reactants have been converted to products.
C) all products have been removed from the reaction mixture.
D) the catalyst has been used up.
E) the rate of the forward reaction equals the rate of the reverse reaction.
Q:
If 25.0 mL of a 0.800 M KCl solution is diluted to a final volume of 100. mL, the new concentration is ________.
Q:
Using a kidney machine to remove waste products from the blood is known as ________.
A) osmosis
B) osmolysis
C) autolysis
D) hemolysis
E) hemodialysis
Q:
Methanol, CH3OH, can be classified as a ________.
A) gas
B) solid
C) weak electrolyte
D) strong electrolyte
E) nonelectrolyte
Q:
NaCl can be classified as a ________.
A) gas
B) liquid
C) weak electrolyte
D) strong electrolyte
E) nonelectrolyte
Q:
0.50 mole of KCl is added to 2.0 kg of water. The boiling point of the solution will be ________ the boiling point of pure water.
A) higher than
B) lower than
C) the same as
Q:
An aqueous mixture containing starch (a colloid), NaCl, glucose, and albumin (a colloid) is placed in a dialyzing bag and immersed in distilled water. Which of the following correctly describes the location of the indicated substance after dialysis?
A) albumin, inside
B) starch outside
C) albumin inside and outside
D) water inside only
E) starch inside and outside
Q:
Which solution is isotonic to a red blood cell?
A) water
B) 0.5% NaCl
C) 2% glucose
D) 0.9% NaCl
E) 10% glucose
Q:
During the process of diluting a solution to a lower concentration,
A) the amount of solute does not change.
B) the amount of solvent does not change.
C) there is more solute in the concentrated solution.
D) the volume of the solution does not change.
E) water is removed from the concentrated solution.
Q:
What volume of a 1.5 M KOH solution is needed to provide 3.0 moles of KOH?
A) 3.0 L
B) 0.50 L
C) 2.0 L
D) 4.5 L
E) 0.22 L
Q:
When 200. mL of water are added to 100. mL of 12% KCl solution the final concentration of KCl is (Assume the volumes add.)
A) 12%.
B) 4.0%.
C) 36%.
D) 6.0%.
E) 8.0%.
Q:
What is the molarity of a solution that contains 17 g of NH3 in 0.50 L of solution?
A) 34 M
B) 2.0 M
C) 0.50 M
D) 0.029 M
E) 1.0 M
Q:
How many grams of glucose are needed to prepare 400. mL of a 2.0%(m/v) glucose solution?
A) 800. g
B) 0.0050 g
C) 8.0 g
D) 2.0 g
E) 200. g
Q:
Rubbing alcohol is 70.% isopropyl alcohol by volume. How many mL of isopropyl alcohol are in a 1 pint (473 mL) container?
A) 70. mL
B) 0.15 mL
C) 680 mL
D) 470 mL
E) 330 mL
Q:
An increase in the temperature of a solution usually
A) increases the boiling point.
B) increases the solubility of a gas in the solution.
C) increases the solubility of a solid solute in the solution.
D) decreases the solubility of a solid solute in the solution.
E) decreases the solubility of a liquid solute in the solution.
Q:
An intravenous replacement solution contains 4.0 mEq/L of Ca2+ ions. How many grams of Ca2+ are in 3.0 L of the solution?
A) 0.24 g
B) 0.80 g
C) 0.40 g
D) 240 g
E) 4.0 g
Q:
How many equivalents are present in 5.0 g of Al3+?
A) 15 Eq
B) 0.56 Eq
C) 0.19 Eq
D) 0.37 Eq
E) 3 Eq
Q:
Water is a polar solvent and hexane (C6H14) is a nonpolar solvent. Which of the following correctly describes the solubility of the solute?
A) mineral oil, soluble in water
B) CaCl2, soluble in hexane
C) NaHCO3, soluble in water
D) CCl4, soluble in water
E) octane, soluble in water
Q:
When KCl dissolves in water
A) the Cl- ions are attracted to dissolved K+ ions.
B) the Cl- ions are attracted to the partially negative oxygen atoms of the water molecule.
C) the K+ ions are attracted to Cl- ions on the KCl crystal.
D) the K+ ions are attracted to the partially negative oxygen atoms of the water molecule.
E) the K+ ions are attracted to the partially positive hydrogen atoms of the water molecule.
Q:
A solution is prepared by dissolving 2 g of KCl in 100 g of H2O. In this solution, H2O is the
A) solute.
B) solvent.
C) solution.
D) solid.
E) ionic compound.
Q:
Which of the following molecules can form hydrogen bonds?
A) CH4
B) NaH
C) NH3
D) BH3
E) HI
Q:
STP stands for 25 C and 760 mmHg.