Gas Laws
A gas occupies 3.50 L at 1.20 atm. The gas is compressed to 2.10 L at constant temperature. What is the new pressure?
P1V1=P2V2
(1.20)(3.50)=P2(2.10)
P2=4.2/2.1
P2=2.00 atm
What happens to the rate of a reaction when the temperature increases, assuming all other conditions remain constant?
The reaction rate increases because particles have more kinetic energy, causing more frequent and energetic collisions.
X (g) + Q (g) -> R (g) + Z (g)
The reaction represented above is found to be second order with respect toX and zero order with respect to Z
What happens to the rate of the reaction when [X] is doubled and [Q] is halved?
It increases by a factor of 4
Balance the equation by filling in the correct coefficients for each substance.
N2H4(l) + O2(g) → NO2(g) + H2O(g)
1, 3, 2, 2
Which periodic trend generally increases from left to right across a period?
Ionization energy, electronegativity
A gas occupies 2.75 L at 25.0°C. To what temperature must it be heated for its volume to reach 4.00 L, assuming constant pressure?
T1/V1=T2/V2
25.0+273=298.15 K
T2=(V2T1)/V1
T2=(4.00*298)/2.75
T2=433.5 K or 160.5 C
A reaction produces 0.80 mol of product in 40.0 s. What is the average rate of product formation?
Rate=0.80 mol/ 40 s
= 0.020 mol/s
The rate law for a particular reaction is rate = k[X]^2. In an experiment, the initial rate of the reaction is determined to be .080 mol/ (L*s) when the initial concentration of X is .20 mol/L.
What is the value of the rate constant, k, for the reaction?
k = rate/ [x]^2
k= 2.0 L/ (mol s)
How many oxygen atoms are on the left side of the following chemical equation?
Pb(NO3)2 + 2NaOH → Pb(OH)2 + 2NaNO3
8
What is the molar mass of Ca(NO₃)₂?
Ca = 40.08 g/mol
N =14.01 g/mol
O = 16.00 g/mol
164.10 g/mol
A 12.0 g sample of O₂ is placed in a 5.00 L container at 35.0°C. What pressure does the O₂ exert?
n= 12.0/32.0 =0.375 mol
p=(nRT)/V = (.375 mol * .0821 * 308)/5
=1.90 atm
For a reaction with the rate law
Rate=k[A]^2
the rate is 0.036 M/s when [A]=0.20 M. What is the value and unit of the rate constant k?
Rate=k[A]^2
k=Rate/[A]^2
k= .90 M-1 S-1
The radioisotope I-123 decays to Te-123 with a half-life of 13.2 hours.
If a sample initially contains 7.90 mg of I-123, what mass of I-123 remains after 8.00 hours?
Write your answer using three significant figures.
m = m₀(1/2)^(t/t₁/₂)
Substitute the values:
m = (7.90 mg)(1/2)^(8.00 h / 13.2 h)
m = (7.90 mg)(1/2)^0.606
m = (7.90 mg)(0.656)
m = 5.18 mg
The following equation represents the combustion of benzene (C6H6) with oxygen gas in the atmosphere.
Balance the equation by filling in the correct coefficients for each substance.
C6H6(l) + O2(g) → CO2(g) + H2O(g)
1, 15, 12, 6
A solution contains 0.250 mol of NaCl dissolved in 500.0 mL of solution. What is its molarity?
M = mol/L
M = 0.250 mol / 0.5000 L
Answer: 0.500 M
Hydrogen gas is collected over water at 25.0°C. The total pressure is 752 torr, and the vapor pressure of water at 25°C is 23.8 torr. What is the partial pressure of H₂?
PH2=752−23.8=728.2 torr
Given the following information, what would the overall order of the reaction be?
R= k[C6H5N2Cl][H2O]^0
1
SO₂Cl₂(g) → SO₂(g) + Cl₂(g)
The first-order decomposition of SO2Cl2(g) is represented by the equation above. At a certain temperature, the partial pressure of SO2Cl2(g) in a sealed vessel falls from 1.0 atm to 0.25 atm over 18 hours.
What is the half-life of the decomposition reaction?
9 hours
Complete the statements to describe the energy changes that take place during a chemical reaction.
input, release
What is the net ionic equation when aqueous AgNO₃ and NaCl are mixed?
Ag⁺(aq) + Cl⁻(aq) → AgCl(s)
A 4.00 L sample of gas at 1.25 atm and 27.0°C is compressed to 2.50 L and heated to 127.0°C. What is the final pressure?
(P1V1)/T1=(P2V2)/T2
(1.25 atm * 4.00 L * 400.15 K)/( 300.15K * 2.5 L)
=2.67 atm
Which of the following are true of reaction rates?
I. The overall rate law is determined by the fastest step of a reaction
II. The presence of a catalyst will increase the number of molecules entering the transition state
III. An increase in temperature will increase the rate of a reaction
IV. Increasing the concentration of reactants will increase the rate at which products yield
II + III only
MgCO3(s) + 2HCl(aq) → MgCl2(aq) + H2O(l) + CO2(g)
A student is studying the kinetics of the reaction represented above. In two separate trials, the student places a 0.95 g sample of MgCO3(s) in excess HCl(aq) and records the time required for the reaction to go to completion. In trial 1, the sample is a single piece of MgCO3(s). In trial 2, the sample consists of powdered MgCO3(s).
Which of the reactions is expected to have the longer reaction time?
Reaction in trial 1
In photosynthesis, plants absorb energy from the sun to convert carbon dioxide and water into glucose and oxygen.
Complete the statements.
Endothermic, greater than, decrease
A 5.00 g sample of CaCO₃ reacts with excess HCl according to:
CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g)
What mass of CO₂ can theoretically be produced?
Molar mass of CaCO₃:
40.08 + 12.01 + 3(16.00) = 100.09 g/mol
Moles of CaCO₃:
5.00 g / 100.09 g/mol = 0.04996 mol
0.04996 mol CaCO₃ = 0.04996 mol CO₂
Molar mass of CO₂:
12.01 + 2(16.00) = 44.01 g/mol
Mass:
0.04996 mol × 44.01 g/mol = 2.20 g
Answer: 2.20 g CO₂