How to tell if a reaction is exothermic or endothermic from an equation?
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From a reaction equation, check the enthalpy change (ΔH). Negative ΔH represents an exothermic reaction (heat producing) while positive ΔH relates to endothermic reaction (heat absorbing). Other methods include reaction diagrams, bond energies, and Hess's Law.
Explanation:An exothermic reaction, which produces heat, will have a negative ΔH, as the bonds in the products are stronger than the bonds in the reactants. This implies that energy is released during the reaction. For instance, when heat (q) is negative in a calorimetric determination, this suggests an exothermic process is taking place, and thermal energy is transferred from the system to its surroundings.
On the other hand, an endothermic reaction, which consumes heat, will have a positive ΔH, as the bonds in the products are weaker than the ones in the reactants. This indicates that energy is absorbed during the reaction. If heat (q) is positive in a calorimetric determination, it signifies that an endothermic process is happening, with thermal energy being transferred from the surroundings to the system.
Furthermore, reaction diagrams, bond energies, and Hess's Law can be applied to predict and calculate the enthalpy changes for reactions, thus determining whether they are exothermic or endothermic.
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Related Questions
What is produced when benzene reacts with chlorine in the presence of an iron catalyst?
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Mary performs this calculation (3.0)(2.0) how many significant figures should her answer have?
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Mary performs this calculation (3.0)(2.0). Her answer have two significant figure.
Hence, option B is correct answer.
What is Significant Figure ?Significant Figure is used to identify a number that is presented in the form of digits.
What are some rules for significant figures ?All the non-zero digits are significant. Example 186452 has six significant digit. Every zeros which occur between the any two non-zero digits are significant. Example 102.0065 has seven significant digits. Every zeros which are on right of a decimal point and left of a non-zero is never significant. Example 0.00654 has three significant digits. Every zero which are right of a number is significant. Example 5.0 has two significant digits.Mary perform this calculation (3.0) (2.0) and get the result 6.0 which has 2 significant digits.
Thus, from above conclusion we can say that Mary performs this calculation (3.0)(2.0). Her answer have two significant figure.
Hence, option B is correct answer.
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What reaction shows one element taking the place of another in a compound?
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Which of the following would have the highest viscosity? water honey salad oil alcohol
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Which of the following is not true regarding carbon? Carbon 12 is radioactive. Carbon can form long chains and rings. Carbon will bond with other carbon atoms. Carbon will readily bond with hydrogen and oxygen
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Answer: Carbon 12 is radioactive
Explanation: Carbon has 3 isotopes out ofwhich carbon 12 isotope has high abundance and carbon 14 has least abundnace in nature.
Thus, Carbon 12 is not radioactive instead Carbon 14 is radioactive.
Carbon is the only element which has the highest ability to form long chains and rings with carbon atom itself. This property is known is CATENATION.
Although sulphur and phosphorus are also known to have the property of the catenation but the carbon has the highest ability.
Yes , carbon can easily and readily bond with hydrogen forming CH4 and the long series. And with oxygen it can form CO2 through covalent bonding.
Which sentence correctly sequences the underlined verbs? We will not receive the final pieces that we needed to complete the collection. We will not receive the final pieces that we had needed to complete the collection. We have not received the final pieces that we will need to complete the collection.
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The sentence that correctly sequences the underlined verbs is: "We have not received the final pieces that we will need to complete the collection."
A verb is a word that expresses an action, occurrence, or state of being.
This sentence correctly uses the present perfect tense ("have not received") to indicate that the action of receiving the final pieces is still ongoing, and it uses the future tense ("will need") to indicate that the pieces are necessary for a future action (completing the collection).
Therefore, "We have not received the final pieces that we will need to complete the collection." is the sentence that correctly sequence the underlined verb.
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The stomach lining is made up of deep muscular grooves. How do you think these structures help the stomach to break down food
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Problem page write a balanced half-reaction for the reduction of solid manganese dioxide mno2 to manganese ion mn 2 in acidic aqueous solution. be sure to add physical state symbols where appropriate.
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In a reduction reaction, some electrons are gained by the substance being reduced. The balanced half-reaction to this would be:
MnO2(s) + 4 H+ (aq) + 2e ---> Mn^2+ (aq) + 2 H2O (aq)
It is called balanced reaction since the number of each element in the left side is equal to the number of each element on the right side.
The balanced half-reaction for the reduction of solid manganese dioxide (MnO2) to manganese ion (Mn^2+) in acidic aqueous solution is: 2MnO2 (s) + 4H+ (aq) + 2e- -> Mn^2+ (aq) + 2H2O (l).
Explanation:The balanced half-reaction for the reduction of solid manganese dioxide (MnO2) to manganese ion (Mn^2+) in acidic aqueous solution is:
2MnO2 (s) + 4H+ (aq) + 2e- → Mn^2+ (aq) + 2H2O (l)
In this reaction, the solid manganese dioxide is reduced to manganese ion by gaining two electrons, and four hydrogen ions are involved in the reaction to balance the charges.
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If poison is suspected in deaths how would you proceed with the investigation
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What 3 characteristics of matter does chemistry deal with?
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1) Composition
The composition of matter helps determine how it will behave chemically and physically, and is studied in chemistry
2) Structure
The structure of a certain element or compound also governs how the substance behaves, making it another vital aspect of chemistry
3) Behavior
The behavior of substances is studied in order to have explanations presented for it, expanding our understanding.
What is the molecular weight of one mole of H2CO3? g/mole
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Answer:
The answer to the question is 62.026.
If r⃗ =bt2i^+ct3j^, where b and c are positive constants, when does the velocity vector make an angle of 45.0∘ with the x- and y-axes?
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The velocity function is the derivative of the displacement:
v = r' = 2bti + 3ct2j meter / second
Now, for the velocity vector make an angle of 45.0∘ with the x- and y-axes, the i and j components have to be equal:
2bt = 3ct2 (Now solve for t)
2bt = t (3ct)
either t = zero (rejected)
or t = 2b / 3c seconds (accepted)
The velocity vector for r⟶ = bt^2î + ct^3ï makes an angle of 45 degrees with the x- and y-axes when the time t equals 2b/(3c), found by setting the magnitudes of the x and y components of the velocity vector equal to each other.
Explanation:To determine when the velocity vector makes an angle of 45 degrees with the x- and y-axes for the given position vector r⟶ = bt^2î + ct^3ï, where b and c are positive constants, we first need to find the velocity vector by differentiating the position vector with respect to time.
The velocity vector v⟶ is given by: v⟶ = dr⟶/dt = 2btî + 3ct^2ï. An angle of 45 degrees between the velocity vector and the axes means the components along the x- and y-axes must be equal. This occurs when 2bt = 3ct^2, which simplifies to t = 2b/(3c). Therefore, the velocity vector makes a 45-degree angle with the axes at this specific time t.
Radiocarbon measurements made in 1988 on the shroud of turin showed a decay rate of 14.2 disintegrations/min per gram of carbon. this is in comparison to the decay rate in the then current living organisms of 15.3 disintegrations/min per gram of carbon. given a half-life of 5730 years for carbon-14, what year is the artifact from?
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A = A₀exp(-k*t)
Where k is the radioactive decay constant and related to half-life as:
t(half) = ln(2)/k
Substituting k from the second equation, and putting the values:
14.2 = 15.3 * exp(-ln(2)* t / 5,730)
t = 617 years
The artifact is 617 years old, which means it is from 1371.
The total bonding energy for the products of a reaction is 2535 kJ/mol and the bonding energy of the reactants is 1375 kJ/mol. Calculate the change in enthalpy, and classify the reaction as endothermic or exothermic.
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the reaction is exothermic as enthalpy change is negative
Answer is: 1160 kJ/mol, endothermic.
the change in enthalpy = the total bonding energy for the products of a reaction - the bonding energy of the reactants.
the change in enthalpy = 2535 kJ/mol - 1375 kJ/mol.
the change in enthalpy = 1160 kJ/mol.
There are two types of reaction:
1) endothermic reaction (chemical reaction that absorbs more energy than it releases).
2) exothermic reaction (chemical reaction that releases more energy than it absorbs).
Silver tarnishes as silver metal reacts with hydrogen sulfide, H2S, in the air. In this reaction, dark silver sulfide, Au2S, covers the surface of silver. When silver is polished, this coating of silver sulfide can be removed from the surface. This makes the silver shiny again. Enter the coefficients that balance the tarnishing reaction equation. (Type 1 for no coefficient.)Ag(s) + H2S(g) → Ag2S(s) + H2(g)
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Balanced the tarnishing equation:
2Ag(s) + 1H₂S(g) → 1Ag₂S(s) + 1H₂(g).
According to principle of mass conservation, number of atoms must be equal on both side of balanced chemical reaction.
There are two silver atoms, two hydrogen atoms and one sulfur atom on both side of balanced chemical reaction.
The coefficients that will balance the tarnishing reaction equation are: 2, 1, 1,1
What is a chemical equationChemical equations are representations of chemical reactions using symbols and formula of the reactants and products.
The reactants are located on the left side while the products are located on the right side.
Reactants —> Products
The balancing of chemical equations follows the law of conservation of matter which states that matter can neither be created nor destroyed during a chemical reaction but can be transferred from one form to another.
Thus, we can obtain the coefficients that will balance the tarnishing reaction equation by simply balancing the equation:
How to balance the equationAg(s) + H₂S(g) → Ag₂S(s) + H₂(g)
There are 2 atoms of Ag on the right side and 1 atom on the left side. It can be balanced by writing 2 before Ag as shown below:
2Ag(s) + H₂S(g) → Ag₂S(s) + H₂(g)
Thus, the equation is balanced.
The coefficients are: 2, 1, 1, 1
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What element is oxidized in the following reaction? Zn + CuSO4 yields ZnSO4 + Cu
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Note: oxidation numbers are very similar to ionic charges, or charges that form as metals and nonmetals, undergo chemical bonding.
1) To note down the oxidation numbers for all elements/atoms in the substances, and then observe that if it is increasing then it is being oxidized, if it is reducing then it would be being reduced.
Zn + CuSO4 -> ZnSO4 + Cu
O +2 -2 -> +2 -2 0
Ignore the -2 as these are spectator ions that do not undergo the change, and are not part of the main reaction occurring.
Here we can see that Zn goes from 0 to +2, thus it would be oxidized, while Cu goes from +2 to 0, thus is reduced.
An element is said to be oxidized when they chemically react with an oxygen atom. In the reaction between zinc and copper sulfate, the zinc element is said to be oxidized.
What is oxidation?In a redox reaction the atoms and molecules losses and gains electron to change their oxidation state by completely transferring their electrons to another atom in the reaction mixture.
Oxidation is the process of redox where the atom losses its electron which can be said as an increase in its oxidation number by giving away its electron or by the addition of oxygen.
The balanced reaction is given as,
Zn + CuSO₄ → ZnSO₄ + Cu
Here, the oxidation number of zinc changes from 0 to +2, and of copper from +2 to 0. It can be inferred that zinc got oxidized, while copper got reduced.
Therefore, in the reaction zinc got oxidized.
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In a combustion reaction, 46.0g of ethanol reacts with 96.0 g of oxygen to produce water and carbon dioxide. If 54.0 g of water is produced, what mass of carbon dioxide is produced?
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Applying this law to the above problem, we find that:
Total mass of reactants = 46 + 96 = 142 grams
This means that the total mass of products (water + carbon dioxide) should be also 142 grams
Since 52 grams of water is produced, therefore,
mass of carbon dioxide = 142 - 52 = 90 grams
Final answer:
The mass of carbon dioxide produced in the combustion reaction of ethanol with oxygen, given that 54.0 g of water is produced, is 88.0 g.
Explanation:
In a combustion reaction of ethanol (C₂H₅OH), which reacts with oxygen (O₂) to produce water (H₂O) and carbon dioxide (CO₂), the mass of carbon dioxide produced can be calculated using the law of conservation of mass. The balanced chemical equation for the combustion of ethanol is:
C₂H₅OH (l) + 3O₂ (g) → 2CO₂ (g) + 3H₂O (g)
Given 46.0 g of ethanol reacts with 96.0 g of oxygen, and 54.0 g of water is produced, we can deduce the mass of carbon dioxide. By the conservation of mass, the total mass of reactants must be equal to the total mass of products:
Mass of reactants = Mass of products
46.0 g (ethanol) + 96.0 g (oxygen) = Mass of water + Mass of carbon dioxide
142.0 g (total reactants) = 54.0 g (water) + Mass of carbon dioxide
Mass of carbon dioxide = 142.0 g - 54.0 g = 88.0 g of CO₂
Therefore, the mass of carbon dioxide produced in this reaction is 88.0 g.
A voltaic cell consists of a nickel electrode in a solution containing Ni2+ ions, and a copper electrode in a solution containing Cu2+ ions. Which is the cell potential? a. E subscript c e l l space end subscript superscript 0 space end superscript equals minus 0.59 V b. E subscript c e l l space end subscript superscript 0 space end superscript equals plus 0.59 V c. E subscript c e l l space end subscript superscript 0 space end superscript equals minus 0.09 V d. E subscript c e l l space end subscript superscript 0 space end superscript equals plus 0.09 V
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Cu⁺² + 2e → Cu; E° = 0.34 V
Ni⁺² + 2e → Ni; E° = - 0.23 V
In order to determine the potential of the cell, we find the difference between the two values. For this:
E(cell) = 0.34 - (-0.23)
E(cell) = 0.57 V
The second option is correct. (The difference in values is due to different values in literature, and it is negligible)
The cell potential of a voltaic cell depends on the difference in reduction potential between the two half-cells. In this case, the copper electrode has a higher reduction potential than the nickel electrode, resulting in a positive cell potential of +0.59 V.
Explanation:The cell potential of a voltaic cell can be determined by the difference in reduction potential between the two half-cells. In this case, the reduction potential of copper is higher than that of nickel. The copper electrode will be reduced while the nickel electrode will be oxidized. The standard cell potential for this voltaic cell is +0.59 V. Therefore, the correct answer is option b) Ecell0 = +0.59 V.
10g of an unknown compound are added to water to form a 7.89 molar solution. if 2 liters of solution are present, what is the molar mass of the unknown compound?
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molarity equation is M = Moles of solute / Liters of solution
7.89 = Moles of solute / 2
(7.89)(2). The question asks for the molar mass which is defined as g/mol. Dividing would give you the unknown compound.
MM = 10g / (7.89)(2)
To calculate the molar mass of the unknown compound, multiply the solution's molarity (7.89 M) by the volume in liters (2 L) to get the moles of solute, then divide the mass of the compound (10 g) by the calculated moles. The molar mass is found to be approximately 0.63 g/mol.
Explanation:To determine the molar mass of the unknown compound, we first need to calculate the number of moles of the solute that was dissolved in water to form the 7.89 M solution.
Molarity (M) of a solution is given by the number of moles of solute per liter of solution. Since we have a 7.89 M solution and the volume of the solution is 2 liters, we can calculate the number of moles:
Number of moles = Molarity × Volume = 7.89 moles/L × 2 L = 15.78 moles
Next, we use the mass of the unknown compound (10 g) to find its molar mass:
Molar mass = Mass of the compound / Number of moles = 10 g / 15.78 moles
Finally, when we perform this division, we find that the molar mass of the unknown compound is approximately:
Molar mass = 0.63 g/mol
Therefore, the molar mass of the unknown compound is 0.63 g/mol.
Which factor is generally responsible for high melting points?
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Answer:
High intermolecular forces of attraction.
Explanation:
When the molecules are attracted to each other, it takes more energy (heat) to break that attraction apart. In order to take a substance from a solid to a liquid, you must break these attractions.
How can a sample of uranium-235 that has critical mass be induced to react? it must be spilt with a laser. it must be fused to a helium nucleus. it must be bombarded with neutrons. it must be shot with light speed electrons?
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Calculate the mass of o2 produced by the decomposition of kclo3 by heating in the presence of manganese dioxide
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2KClO3 = 2KCl + 3O2
To determine the mass of oxygen gas that is produced from a given amount of potassium chlorate, we use the initial amount of the reactant and use the relations from the reaction of the substances involved. However, from the problem, the amount of reactant is not given. We assume 1 g of potassium chlorate.
1 g KClO3 ( 1 mol / 122.55 g ) ( 3 mol O2 / 2 mol KClO3 ) ( 32 g O2 / 1 mol O2 ) = 0.3917 g of O2 produced.
If the given amount of the reactant is not 1 g, then you can change the value of the mass from the calculation and evaluate the new value of oxygen gas produced.
The drawing shows sodium and chloride ions positioned at the corners of a cube that is part of the crystal structure of sodium chloride (common table salt). the edges of the cube are each 0.281 nm (1 nm = 1 nanometer = 10−9 m) in length. what is the value of the angle θ the in the drawing?
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To solve for this problem, first we have to calculate for the diagonal or the hypotenuse on the bottom face of the cube. We can do this by using the hypotenuse formula. Since all sides are of equal lengths therefore:
c^2 = a^2 + b^2
a = b
c^2 = 2 a^2
where a = 0.281 nm therefore:
c^2 = 2 (0.281 nm)^2
c = 0.3974 nm
Now using the diagonal and the one vertical side of the cube which is still equivalent to a, we use the tan function to find for the angle θ.
tan θ = opposite side / adjacent side
tan θ = a / c
θ = tan^-1 (0.281 / 0.3974)
θ = 35.26°
Final answer:
The crystal structure of sodium chloride and the calculation of the force on a lithium ion in a NaCl crystal lattice involves applying Coulomb's law to consider contributions of electrostatic forces from neighboring ions.
Explanation:
The question concerns the crystal structure of sodium chloride (NaCl), commonly known as table salt, and involves calculating the force on a lithium ion in the crystal lattice with defects. The edges of the cube in the NaCl crystal are provided as 0.281 nm, which is the distance between neighboring ions, and it is given that the ions form a face-centered cubic (FCC) structure. To find the angle θ in the drawing, one would need a diagram to assess the geometry between the ions.
As for the force on the lithium ion, you would apply Coulomb's law to calculate the electrostatic force exerted on it by its neighboring charged ions. Each neighboring ion contributes a vector force, and the total force on the lithium ion is the vector sum of these individual forces.
Which of the following metals is the most stable?
A. Potassium
B. Zinc
C. Silver
D. Gold
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Answer:
gold
Explanation:
Among the options listed, gold is the most stable metal. It's resistant to oxidation and corrosion, unlike the other metals. This is why it's often found in its native form and used for various purposes.
Explanation:The stability of a metal is determined by its resistance to oxidation or corrosion, and by this standard, gold (option D) is the most stable metal among those listed. Gold does not easily react with other substances in the environment, making it highly resistant to corrosion and oxidation. This property is why gold is often found in its native form in nature, not combined with other elements, and why it's used for jewelry and in various industrial applications.
On the other hand, metals like potassium (option A) are highly reactive, readily oxidizing in air or reacting violently with water. Zinc (option B) and silver (option C) are less reactive than potassium, but still more reactive compared to gold.
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"if the average global intake of vegetables is 2,300 calories per day, how many liters of water are needed to produce these vegetable calories"
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Calculate the vapor pressure of water above a solution prepared by dissolving 28.5 g of glycerin (c3h8o3) in 135 g of water at 343 k. (the vapor pressure of water at 343 k is 233.7 torr.)
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The vapor pressure of water above a solution prepared by dissolving glycerin in water at 343K is equal to the vapor pressure of pure water at the same temperature, which is 233.7 Torr, as glycerin is nonvolatile.
Explanation:In this problem, we're asked to calculate the vapor pressure of water above a solution of glycerin in water. The key concept here is Raoult's Law, which states that the vapor pressure of a solvent above a solution (in this case water) is directly proportional to the mole fraction of that solvent in the solution.
Glycerin (C3H8O3) is essentially nonvolatile, meaning it does not contribute to the vapor pressure. Therefore, the vapor pressure of the solvent (water) is not altered by the addition of the glycerin. Essentially, the vapor pressure of the water in the solution is the same as the vapor pressure of pure water at the same temperature.
The given vapor pressure of pure water at 343 K is 233.7 Torr. Hence, the vapor pressure of water above the solution prepared by dissolving 28.5 g of glycerin in 135 g of water at the same temperature is also 233.7 Torr.
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The vapor pressure of water above a solution containing 28.5 g of glycerin and 135 g of water at 343 K is calculated using Raoult's Law. The resulting vapor pressure is 224.352 torr.
Calculation of Vapor Pressure
To calculate the vapor pressure of water above a solution containing 28.5 g of glycerin ([tex]C_3H_8O_3[/tex]) and 135 g of water at 343 K, we use Raoult's Law.
Molar mass of glycerin ([tex]C_3H_8O_3[/tex]) = 3(12.01) + 8(1.008) + 3(16.00) = 92.094 g/mol
Moles of glycerin =
28.5 g / 92.094 g/mol = 0.309 moles
Molar mass of water (H2O) = 2(1.008) + 16.00 = 18.016 g/mol
Moles of water =
135 g / 18.016 g/mol = 7.495 moles
Mole fraction of water ([tex]X_{water[/tex]) = moles of water / (moles of water + moles of glycerin)
[tex]X_{water[/tex] = 7.495 moles / (7.495 + 0.309) = 0.960
Use Raoult's Law to find the vapor pressure of the solution.Raoult's Law:
[tex]P_{solution[/tex]= [tex]X_{water[/tex]* [tex]P_{water[/tex]
[tex]P_{solution[/tex]= 0.960 * 233.7 torr = 224.352 torr
Therefore, the vapor pressure of water above the solution at 343 K is 224.352 torr.
A reconstituted solution containing 500 mg of ganciclovir in 20 ml of sterile water for injection is added to 500 ml of 5% dextrose in water. the infusion is to be administered over 2 hours. if the infusion set delivers 15 drops/ml, what should the flow rate be to administer the bag over the designated time interval?
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Usually it is counted the number of drops per minute, so I will aim to that.
1) Calculate the total volume.
Assuming additive volumes => final volume = volume of sterile water + volume of the dextrose solution
Final volume = 20 ml + 500 ml = 520 ml.
2) Calculate the number of drops in 520 ml, given that there are 15 drops in 1 ml:
=> 520 ml * 15 drops / ml = 7800 drops.
3) That must be administered over 2 hours, which is 120 minutes.
So, calculate the flow rate as the number of drops divided by the time in minutes:
flow rate = 7800 drops / 120 minutes = 65 drops / minute.
Answer: 65 drops / minute
Radioactive decay occurs when two nuclei are smashed into each other and combine to form a much larger nucleus and release a vast amount of energy.
True
False
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A car travels at 15 kilometers west in 10 minutes after reaching the destination the car travels back to the starting point again taking 5 minutes what is the average velocity of the car
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Answer: D 2.0 meters/second
Explanation:
A 0.465 g sample of an unknown compound occupies 245 mL at 298 K and 1.22 atm. What is the molar mass of the unknown compound?
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PV= nRT
PV = (m/Mr) RT The molar mass of the unknown compound is : 38.0 g/mol
Mr = mRT / PV = 0.465 g x 0.08206 L * atm * K⁻¹ mol ⁻¹ x 298 K / 1.22 atm x 0.245 L = 38.0 g / mol
everything else but G / Mol are cancelled out.