Chemical reaction equations
What is the net ionic equation for the following balanced reaction?
Pb(NO3)2(aq)+H2SO4(aq)⟶PbSO4(s)+2HNO3(aq)
What is
Pb2+(aq)+SO42-(aq)→PbSO4(s)
(Identify the spectator ions which are the ions that do not change during their reaction or that are the same on both sides. NO3- and H+ appear on both sides so that can be removed. Pb2+(aq)+SO42-(aq)→PbSO4(s) are the essential parts of the reaction which is the formation of the precipitate PbSO4(s).)
A piece of unknown solid substance weighs 437.2 g, and requires 8460 J to increase its temperature from 19.3 °C to 68.9 °C. What is the specific heat of the substance?
What is
0.390J/g°C
(To find the specific heat of the substance, we can use the formula: Q=m⋅c⋅ΔT Q=8460J (the heat energy required). m=437.2 g (the mass of the substance). ΔT=Tfinal−Tinitial where Tfinal= 68.9∘C and Tinitial=19.3∘C subtract Tinitial by Tfinal to get 49.6∘C.
We want to solve for specific heat so rearrange the formula: c=Q/(m⋅ΔT). Finally, substitute values in the formula to get the answer 0.390J/g°C)
What is the n, l, and ml degeneracy of 5d?
What is
n=5, l=2, ml degeneracy=5
(To determine the degeneracy of the 5d orbital, we need to identify the quantum numbers n, l, and ml.
1. Principal quantum number (n):
For the 5d orbital, n=5
2. Azimuthal quantum number (l):
For a d-orbital, l=2 since l corresponds to the type of orbital (s, p, d, f), with l=0 for s, l=1for p, l=2 for d, and l=3 for f.
3. Magnetic quantum number (ml):
The ml values range from −l to +l, including zero. For l=2, ml can take values: ml=−2,−1,0,+1,+2This gives a total of 5 possible mlm_lml values.
Degeneracy:
The degeneracy of an orbital is the number of available ml values. For l=2 , the degeneracy is 5, because there are 5 possible values for ml.)
What is the energy in joules of the photon emitted when an electron in a hydrogen atom moves from the n=6 orbit to the n=4 orbit?
What is
ΔE= 7.566 × 10-20 J
( To calculate the energy of the photon emitted when an electron in a hydrogen atom transitions from the n=6 orbit to the n=4orbit using the given equation:
ΔE= E1 − E2 = 2.179 × 10-18 (1/n12−1/n22)Where:
E1 and E2 are the energy levels corresponding to the initial and final orbits.
n1=6 (initial orbit) and n2=(final orbit).
The constant 2.179×10-18 is the energy constant for the hydrogen atom (in joules).
Step 1: Substitute the values into the equation
ΔE=2.179×10-18(162−142)Step 2: Calculate the individual fractions
1/62=1/36, 1/42=1/16 Now subtract:
1/36 − 1/16 =4/144 − 9/144=−5/144
Step 3: Multiply by the constant
ΔE=2.179×10-18×−5/144
ΔE=−7.566×10-20J
The negative sign indicates that energy is released (photon emitted) when the electron moves from a higher energy level to a lower one. Therefore, the energy of the photon emitted is: 7.566 × 10-20 J)
is the following reaction an endothermic or exothermic process? is heat being absorbed or released? HCl(aq)+NaOH(aq)⟶NaCl(aq)+H2O(l)ΔH°=−58kJ
What is
exothermic. heat is released.
(A reaction is exothermic if it releases heat. This means that the products of the reaction have lower energy than the reactants.
A reaction is endothermic if it absorbs heat. This means that the products have higher energy than the reactants.
The negative sign in ΔH∘=−58 kJ indicates that the reaction is exothermic. In an exothermic reaction, heat is released to the surroundings.)
What is the net ionic equation for the reaction between potassium sulfate and barium nitrate?
What is
Ba2+(aq)+SO2-4(aq)⟶BaSO4(s)
(Identify the spectator ions which are the ions that do not change during their reaction or that are the same on both sides. K+ and NO3- appear on both sides so that can be removed. Ba2+(aq)+SO2-4(aq)⟶BaSO4(s) are the essential parts of the reaction which is the formation of the precipitate BaSO4(s).)
How much will the temperature of a cup (180 g) of coffee at 95 °C be reduced when a 45 g silver spoon (specific heat 0.24 J/g °C) at 25 °C is placed in the coffee and the two are allowed to reach the same temperature? Assume that the coffee has the same density and specific heat as water.
What is
1.0°C
(You have 180 g of coffee at 95°C and a 45 g silver spoon at 25°C. When you put the spoon into the coffee, heat will transfer from the hot coffee to the cooler spoon until both reach the same temperature. We need to figure out how much the coffee’s temperature will drop.
The heat lost by the coffee will be the same as the heat gained by the spoon because energy is conserved (no energy is lost to the surroundings).
So, we set up this equation:
Heat lost by coffee=Heat gained by spoon
The formula for heat is: Q=m⋅c⋅ΔTQ Where for coffee:
Q= is the heat (energy) transferred.
m=180g (mass).
c= 4.18 ( specific heat of water (how much energy is needed to change the temperature of 1 gram of a substance by 1°C)).
ΔT is the temperature change (final temperature - initial temperature). The coffee loses heat. So the equation for coffee is:
Qcoffee=180 ⋅ 4.18 ⋅ (95−Tfinal) The spoon gains heat. The equation for the spoon is:
Qspoon= 45g ⋅ 0.24J/g°C ⋅ (Tfinal−25)
(0.24J/g°C is the specific heat of silver.)
Now, set the heat lost by the coffee equal to the heat gained by the spoon:
(180 ⋅ 4.18 ⋅ (95−Tfinal))= (45 ⋅ 0.24 ⋅ (Tfinal−25))
We simplify and solve for Tfinal (the final temperature of both the coffee and the spoon). After solving the equation, we find that the final temperature is approximately 94°C.
The coffee started at 95°C, and now the final temperature is 94°C. So, the coffee's temperature drops by:
Temperature reduction=95°C−94°C=1°C The temperature of the coffee will decrease by about 1°C after placing the spoon in it.)
if l=f, what are all possible Magnetic Quantum numbers?
What is
-3, -2, -1, 0, +1,+2,+3
(When l=3 (for an f-orbital), the possible values of the magnetic quantum number (ml) range from −l to +l, including zero. Therefore, for l=3 the possible values are ml=−3,−2,−1,0,+1,+2,+3)
Calculate the de Broglie wavelength of a car with a mass of 1000 kg traveling at a velocity of 30 m/s, assuming it can be modeled as a particle.
What is
λ=2.2 × 10-38 m
(To calculate the de Broglie wavelength of a car, we use the de Broglie wavelength formula:
λ=h/mv Where:
λ is the de Broglie wavelength,
h is Planck's constant (6.626×10-34 J),
m is the mass of the car (1000 kg),
v is the velocity of the car (30 m/s).
Substitute the given values into the formula:
λ=6.626×10-34J*s /1000kg × 30m/s
Perform the calculation:
λ=6.626×10-34/30000
λ=2.2×10-38m)
What is the reducing agent in the following equation
Mg(s)+Ni2+(aq)→Mg2+(aq)+Ni(s)
What is
Mg(s)
(A reducing agent is a substance that donates electrons to another substance, causing the reduction of that substance. In this case:
Mg(s) (magnesium) loses two electrons to become Mg²⁺(aq), undergoing oxidation.
These electrons are transferred to Ni²⁺(aq), reducing it to Ni(s) (nickel).
Since magnesium donates electrons (undergoing oxidation), it acts as the reducing agent in this reaction.)
What is the balanced molecular equation for the reaction between barium hydroxide (Ba(OH)₂) and nitric acid (HNO₃)?
What is
Ba(OH)2(aq)+2HNO3(aq)→Ba(NO3)2(aq)+2H2O(l)
(Ba(OH)2 is a strong base, HNO3 is a strong acid. Ba(OH)2 dissociates into Ba2++2OH- . HNO3 dissociates into H++NO3- . They mix together to form Ba(NO3)2 and H2O(l). this gets us the unbalanced equation Ba(OH)2(aq)+HNO3(aq)→Ba(NO3)2(aq)+H2O(l). there are 3 hydrogens on the left side of the equation and only 2 on the right, to balance the equation put a 2 before HNO3 on the left and a 2 before H2O on the right to get 4 Hydrogens on each side. This completes the balanced molecular equation)
When a 0.740-g sample of trinitrotoluene (TNT), C7H5N2O6, is burned in a bomb calorimeter, the temperature increases from 23.4 °C to 26.9 °C. The heat capacity of the calorimeter is 534 J/°C, and it contains 675 mL of water(the density of water is approximately 1 g/mL). How much heat was produced by the combustion of the TNT sample?
What is
11.7 kJ
(
To find the heat produced by the combustion of TNT in the bomb calorimeter, we need to calculate the total heat absorbed by the calorimeter and the water inside it.
Temperature change (ΔT\Delta TΔT):
The temperature change is 26.9∘C−23.4∘C=3.5∘C
Heat absorbed by the calorimeter:
The heat absorbed by the calorimeter is Qcal=Ccal×ΔT=534×3.5=1879 J
Heat absorbed by the water:
The heat absorbed by the water is Qwater=mwater×cwater×ΔT=675×4.18×3.5=9949.5 J
Total heat produced:
The total heat produced is the sum of both:
Qtotal=1879+9949.5=11828.5 J convert unit J to kJ by dividing by 1000 to get the answer 11.83kJ)
If a shell contains a maximum of 128 electrons, what is the principal quantum number, n?
What is
n=8
(To find the principal quantum number n for a shell that can hold a maximum of 128 electrons, we use the formula for the maximum number of electrons in a shell:
Max electrons=2n2
Given that the shell holds a maximum of 128 electrons, we set up the equation:
2n2=128 Solve for n:
n2 =128/2=64
n=√64=8)
The radio waves used for communication in cell phones have a frequency of about 1.5×109 Hz. What is the energy of one photon in these radio waves?
What is
E= 9.94 × 10-25 J
(To calculate the energy of one photon in the radio waves, we can use the formula:
E=h ⋅ f
Where:
E is the energy of the photon,
h is Planck's constant (6.626×10-34 J*s),
f is the frequency of the radio waves (1.5×109 Hz).
Substitute the given values into the formula:
E=(6.626×10-34 J*s) × (1.5×109 Hz)
multiply:
E=9.94×10-25 J)
which of the following compounds is insoluble
a)AgNO₃
b)BaSO₄
c)NaCH₃COO
d)NH₄OH
What is
b) BaSO4
(AgNO₃ (Silver nitrate): Soluble. Nitrates (NO₃⁻) are generally soluble in water.
BaSO₄ (Barium sulfate): Insoluble. Most sulfate salts are soluble, but barium sulfate is an exception and is known to be highly insoluble in water.
NaCH₃COO (Sodium acetate): Soluble. Sodium salts (Na⁺) and acetate (CH₃COO⁻) are typically soluble in water.
NH₄OH (Ammonium hydroxide): Soluble. Ammonium compounds (NH₄⁺) are generally soluble in water, and ammonium hydroxide is a weak base that dissociates in water.
So, BaSO₄ is the insoluble compound.)
Which of the following reactions is NOT a redox reaction?
(a) 2Ga(l) + 3Br₂(l) → 2GaBr₃(s)
(b) 2H₂O₂(aq) → 2H₂O(l) + O₂(g)
(c) BaCl₂(aq) + K₂SO₄(aq) → BaSO₄(s) + 2KCl(aq)
What is
(c) BaCl₂(aq) + K₂SO₄(aq) → BaSO₄(s) + 2KCl(aq)
( For (a), Ga(l) is in the elemental state, so its oxidation state is 0. Br₂(l) is also in its elemental state, so the oxidation state of Br is 0. In the product, GaBr₃-, Ga has an oxidation state of +3 (since bromine is usually -1 in a compound). Br has an oxidation state of -1 in GaBr₃-. Ga changes from 0 to +3 (oxidation, because it loses electrons). Br changes from 0 to -1 (reduction, because it gains electrons) so this IS a redox reaction. For (b), H₂O₂ (hydrogen peroxide), the oxidation state of oxygen is -1. In H₂O (water), the oxidation state of oxygen is -2. In O₂ (oxygen gas), the oxidation state of oxygen is 0. Oxygen in H₂O₂ goes from -1 to -2 in H₂O (reduction, since it gains electrons). Oxygen in H₂O₂ goes from -1 to 0 in O₂ (oxidation, since it loses electrons). Since oxygen undergoes both reduction and oxidation in this reaction, this IS a redox reaction. For (C) Ba in BaCl₂ has an oxidation state of +2. Cl in BaCl₂ has an oxidation state of -1. K in K₂SO₄ has an oxidation state of +1. SO₄²⁻ in K₂SO₄ has an oxidation state of -2. In the product BaSO₄(s) + 2KCl(aq), all elements have the same oxidation state so this is NOT a redox reaction Instead, it is a precipitation reaction, where the products BaSO₄ precipitate out of solution.
A 70.0-g piece of metal at 80.0 °C is placed in 100 g of water at 22.0 °C contained in a calorimeter. The metal and water come to the same temperature at 24.6 °C. What is the specific heat of the metal?
What is
0.28 J/g°C
(To find the specific heat of the metal, we use the principle of energy conservation:
Find Heat lost by the metal
The heat lost by the metal is:
Qmetal=mmetal ⋅ cmetal ⋅ ΔT
Qmetal=70.0 ⋅ cmetal ⋅ (80.0−24.6)=70.0 ⋅ cmetal ⋅ 55.4
The heat gained by the water is:
Qwater=100⋅4.18⋅(24.6−22.0)=1086.8 J
Set heat lost by metal = heat gained by water
70.0⋅cmetal⋅55.4=1086.8
Solve for cmetal
cmetal=1086.8/ (70.0 ⋅ 55.4)≈0.28 J/g°C)
Which set of quantum numbers is NOT allowed?
(a) n=3, l=1, ml=2, ms=-1/2
(b) n=3, l=2, ml=1, ms=+1/2
(c) n=4, l=3, ml=−2, ms=-1/2
(d) n=2, l=1, ml=1, ms=+1/2
What is
(a) n=3, l=1, ml=2, ms=-1/2
( In the case for n=3,l=1,ml=2,ms=−1/2
ml=2 is invalid because ml must range from −l to +l, so for l=1, ml can only be −1,0,+1-1, 0, +1−1,0,+1.)
When we see light from a neon sign, we are observing radiation from excited neon atoms. If this radiation has a wavelength of 640 nm, what is the energy of the photon being emitted?
What is
E= 3.11 × 10-19 J
(To calculate the energy of the photon emitted by the excited neon atoms, we can use the formula:
E=(h ⋅ c)/λ Where:
E is the energy of the photon,
h is Planck's constant (6.626×10-34J*s),
c is the speed of light (3.00×108 m/s),
Λ is the wavelength of the light
(640 nm=640 × 10-9m).
Substitute the given values into the formula:
E=(6.626×10-34 J*s)×(3.00×108 m/s)/(640×10-9 m)
Perform the calculation:
E=1.9878×10-25/640×10-9
E=3.11×10-19J)
which of these colors has the longest wavelength?
a) red
b) orange
c) green
d) violet
What is
a) red
(According to the Visible light spectrum, the wavelengths of visible light range from approximately 400 nm (violet) to 700 nm (red).)
Which of the following reactions is an acid-base reaction?
a) BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaCl(aq)
b) Mg(OH)₂(s) + 2HCl(aq) → MgCl₂(aq) + 2H₂O(l)
c) Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)
d) AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq)
What is
b) Mg(OH)₂(s) + 2HCl(aq) → MgCl₂(aq) + 2H₂O(l)
((a) This reaction is a precipitation reaction, not an acid-base reaction. BaCl₂ and Na₂SO₄ are ionic compounds in solution. They exchange ions, resulting in the formation of BaSO₄, which is insoluble and precipitates out of the solution, and NaCl, which remains dissolved in solution. There is no transfer of protons (H⁺), so this is not an acid-base reaction.
(b) Mg(OH)₂ is magnesium hydroxide, which is a base (because it contains the hydroxide ion, OH⁻). HCl is hydrochloric acid, a strong acid (because it dissociates completely to release H⁺ ions). In this reaction: The H⁺ ions from HCl react with the OH⁻ ions from Mg(OH)₂, forming water (H₂O), which is characteristic of an acid-base neutralization reaction. MgCl₂ is formed as the salt, but the main feature here is the transfer of protons between the acid and base. Thus, this reaction is an acid-base reaction.
(c) Zn is a metal that reacts with CuSO₄ (copper sulfate) in a redox process. Zinc displaces copper from copper sulfate, and in doing so, zinc is oxidized (loses electrons), and copper is reduced (gains electrons). Since the reaction involves the transfer of electrons (a redox process) and not the transfer of protons (H⁺ ions), this is a redox reaction, not an acid-base reaction. for
(d) AgNO₃ and NaCl are both soluble in water. When mixed, they exchange ions, resulting in the formation of AgCl, which is insoluble and precipitates out, and NaNO₃, which remains dissolved. There is no transfer of protons (H⁺), so this is not an acid-base reaction but a precipitation reaction)
Calculate ΔH for the process Hg2Cl2(s)⟶2Hg(l)+Cl2(g)Hg2Cl2(s)⟶2Hg(l)+Cl2(g)
from the following information:
Hg(l)+Cl2(g)⟶HgCl2(s)ΔH=−224kJ
Hg(l)+HgCl2(s)⟶Hg2Cl2(s)ΔH=−41.2kJ
What is
265 kJ
(We use the given reactions and their enthalpy changes to manipulate them into the desired reaction. The key is to combine the reactions in such a way that they cancel out correctly.
Step 1: Reverse the reactions
Reverse reaction 1:
HgCl2(s)→Hg(l)+Cl2(g),ΔH=+224 kJ
Reverse reaction 2:
Hg2Cl2(s)→Hg(l)+HgCl2(s),ΔH=+41.2 kJ
Step 2: Add the reactions
Hg2Cl2(s)→2Hg(l)+Cl2(g)
Step 3: Add the enthalpies
ΔH=224 kJ+41.2 kJ=+265.2 kJFinal Answer:
ΔH=+265 kJ)
Identify the subshell in which electrons with the following quantum numbers are found: (a) n=3, l =1; (b) n=5, l=3; (c) n=2, l=0.
What is
(a) 3p (b) 5f (c) 2s
(To identify the subshell based on the quantum numbers, we use the following guidelines:
n is the principal quantum number, which indicates the energy level (shell).
l is the azimuthal quantum number, which indicates the type of subshell:
l=0 corresponds to an s subshell.
l=1 corresponds to a p subshell.
l=2 corresponds to a d subshell.
l=3 corresponds to an f subshell.
(a) n=3,l=1: n=3 indicates the third energy level (shell). l=1 corresponds to a p subshell.
Answer: 3p subshell.
(b) n=5,l=3: n=5 indicates the fifth energy level (shell). l=3 corresponds to an f subshell.
Answer: 5f subshell.
(c) n=2,l=0: n=2 indicates the second energy level (shell). l=0 corresponds to an s subshell.
Answer: 2s subshell.)
A sodium streetlight gives off yellow light that has a wavelength of 589 nm. What is the frequency of this light?
What is
5.09×1014s-1
(To find the frequency of the sodium streetlight's yellow light, we can use the formula:
f=c/λ
where:
c is the speed of light (3.00×108 m/s),
λis the wavelength (589 nm, which is 589×10-9m),
f is the frequency.
Substitute the given values into the formula:
f=(3.00×108 m/s)/(589×10-9m)
Perform the division:
f=5.09×1014 s-1)
Determine the oxidation states of the elements in the following compound:
H3PO4
What is
H +1, P +5, O −2;
(This molecule contains:
3 Hydrogens (H) 1 Phosphorus (P) 4 Oxygens (O)
Find the oxidation state of hydrogen (H) In most compounds, hydrogen always has an oxidation state of +1. Since there are 3 hydrogen atoms, each has an oxidation state of +1.
Find the oxidation state of oxygen (O) Oxygen usually has an oxidation state of -2 in most compounds. Since there are 4 oxygen atoms, each has an oxidation state of -2.
Find the oxidation state of phosphorus (P)Now, to find the oxidation state of phosphorus (P), we need to use the rule that says the total oxidation states in a neutral molecule must add up to zero. equation:
The oxidation states of hydrogen: 3 atoms × +1 = +3
The oxidation states of oxygen: 4 atoms × -2 = -8
Now, the oxidation state of phosphorus (P) is unknown( x).
The total oxidation states should add up to 0 (since the molecule is neutral), so: 3(oxidation state of H) + x(oxidation state of P) + 4(oxidation state of O)= 0
Substitute the values we know:
3(+1) + x + 4(−2) =0 Simplify it: 3 + x − 8 =0
Now solve for x: x−5=0
x= +5
So, the oxidation state of phosphorus (P) is +5.
therefore Hydrogen (H) = +1 Phosphorus (P) = +5 Oxygen (O) = -2)