The formation of hydrogen chloride from hydrogen and chlorine is a strongly exothermic reaction. From this, it can be deduced that______.
A. the temperature falls during the reaction
B. Heat is absorbed during reaction
C Hydrogen chloride gas burns readily in air
D Hydrogen chloride gas is not easily decomposed by heat.
My answer is C. A and B are both ruled out since they describe an endothermic reaction. Since an exothermic reaction gives out heat, HCl gas burns readily in air, giving out heat in the process. Is this correct?
When hydrogen and iodine combine to form hydrogen iodide, heat is absorbed. From this, we can deduce that___
A hydrogen and iodine react more rapidly at lower temperature
B the energy involved in making the bonds is less than that involved in breaking the bonds.
C more bonds are broken than formed
D the formation of H-I bonds uses up energy.
My answer is C. there are both signs of exothermic and endothermic reaction. However, HEAT is absorbed, suggesting that at the end of reaction, an endothermic reaction has taken place. In endothermic reaction, it involves the breaking of bonds.
State the type of energy change that takes place when anhydrous sodium carbonate dissolves in water.
Initial temperature of water was 25deg cel. after dissolving in water, temperature of solution is 34deg cel, an increase by 9deg cel.
This is an endothermic reaction. since heat energy is taken in and temperature of SOLUTION rises, hence causing the surrounding to dip in temperature.
Are the explanations correct? If no, please justify. thanks.
Originally posted by bonkysleuth:The formation of hydrogen chloride from hydrogen and chlorine is a strongly exothermic reaction. From this, it can be deduced that______.
A. the temperature falls during the reaction
B. Heat is absorbed during reaction
C Hydrogen chloride gas burns readily in air
D Hydrogen chloride gas is not easily decomposed by heat.
My answer is C. A and B are both ruled out since they describe an endothermic reaction. Since an exothermic reaction gives out heat, HCl gas burns readily in air, giving out heat in the process. Is this correct?
When hydrogen and iodine combine to form hydrogen iodide, heat is absorbed. From this, we can deduce that___
A hydrogen and iodine react more rapidly at lower temperature
B the energy involved in making the bonds is less than that involved in breaking the bonds.
C more bonds are broken than formed
D the formation of H-I bonds uses up energy.
My answer is C. there are both signs of exothermic and endothermic reaction. However, HEAT is absorbed, suggesting that at the end of reaction, an endothermic reaction has taken place. In endothermic reaction, it involves the breaking of bonds.
State the type of energy change that takes place when anhydrous sodium carbonate dissolves in water.
Initial temperature of water was 25deg cel. after dissolving in water, temperature of solution is 34deg cel, an increase by 9deg cel.
This is an endothermic reaction. since heat energy is taken in and temperature of SOLUTION rises, hence causing the surrounding to dip in temperature.
Are the explanations correct? If no, please justify. thanks.
All 3 of your answers are wrong.
The formation of hydrogen chloride from hydrogen and chlorine is a strongly exothermic reaction. From this, it can be deduced that______.
A. the temperature falls during the reaction
B. Heat is absorbed during reaction
C Hydrogen chloride gas burns readily in air
D Hydrogen chloride gas is not easily decomposed by heat.
Correct answer is D. Much heat released implies bonds formed are strong (and/or many). Hence, not easily decomposed (which is not the same as combusted).
When hydrogen and iodine combine to form hydrogen iodide, heat is absorbed. From this, we can deduce that___
A hydrogen and iodine react more rapidly at lower temperature
B the energy involved in making the bonds is less than that involved in breaking the bonds.
C more bonds are broken than formed
D the formation of H-I bonds uses up energy.
Correct answer is B. Since overall, heat is absorbed, means is endothermic reaction means energy taken in during bond breaking exceeds energy given out during bond forming. For option C, you need to draw the Kekule structures of the reactants, intermediates and products, to compare and deduce (in addition, all bonds need to be covalent bonds for a straightfoward comparison, which in this particular reaction they are indeed).
>>> State the type of energy change that takes place when anhydrous sodium carbonate dissolves in water. Initial temperature of water was 25deg cel. after dissolving in water, temperature of solution is 34deg cel, an increase by 9deg cel. <<<
This is an exothermic reaction, since overall (ie. net change), heat energy was given to the environment (ie. the solution, and the thermometer).
Remember the best example of an EXOthermic reaction (in which heat EXits; in contrast to heat ENtering in an ENdothermic reaction), is that of combustion (aka burning), and your hand serves as the environment and thermometer. Your hand feels hot, so it's an exothermic reaction (since heat is transferred from the reactants/reaction to the environment which is your hand).
Originally posted by UltimaOnline:
All 3 of your answers are wrong.
The formation of hydrogen chloride from hydrogen and chlorine is a strongly exothermic reaction. From this, it can be deduced that______.
A. the temperature falls during the reaction
B. Heat is absorbed during reaction
C Hydrogen chloride gas burns readily in air
D Hydrogen chloride gas is not easily decomposed by heat.
Correct answer is D. Much heat released implies bonds formed are strong (and/or many). Hence, not easily decomposed (which is not the same as combusted).
When hydrogen and iodine combine to form hydrogen iodide, heat is absorbed. From this, we can deduce that___
A hydrogen and iodine react more rapidly at lower temperature
B the energy involved in making the bonds is less than that involved in breaking the bonds.
C more bonds are broken than formed
D the formation of H-I bonds uses up energy.
Correct answer is B. Since overall, heat is absorbed, means is endothermic reaction means energy taken in during bond breaking exceeds energy given out during bond forming. For option C, you need to draw the Kekule structures of the reactants, intermediates and products, to compare and deduce (in addition, all bonds need to be covalent bonds for a straightfoward comparison, which in this particular reaction they are indeed).
>>> State the type of energy change that takes place when anhydrous sodium carbonate dissolves in water. Initial temperature of water was 25deg cel. after dissolving in water, temperature of solution is 34deg cel, an increase by 9deg cel. <<<
This is an exothermic reaction, since overall (ie. net change), heat energy was given to the environment (ie. the solution, and the thermometer).
Remember the best example of an EXOthermic reaction (in which heat EXits; in contrast to heat ENtering in an ENdothermic reaction), is that of combustion (aka burning), and your hand serves as the environment and thermometer. Your hand feels hot, so it's an exothermic reaction (since heat is transferred from the reactants/reaction to the environment which is your hand).
Can you please explain to me the first question again? I don't kind of understnad. But doesn't burning GIVE OUT heat to surrounding too?
And the environment in question 3 is referring to the solution or the atmosphere around? Since the temperature of solution increases, heat is taken in by the solution? So shouldn't it be an endothermic reaction? Thankyou
oh yea, does enthalpy change related to temperature? i think i confused both of them in my third question
Originally posted by UltimaOnline:
All 3 of your answers are wrong.
The formation of hydrogen chloride from hydrogen and chlorine is a strongly exothermic reaction. From this, it can be deduced that______.
A. the temperature falls during the reaction
B. Heat is absorbed during reaction
C Hydrogen chloride gas burns readily in air
D Hydrogen chloride gas is not easily decomposed by heat.
Correct answer is D. Much heat released implies bonds formed are strong (and/or many). Hence, not easily decomposed (which is not the same as combusted).
When hydrogen and iodine combine to form hydrogen iodide, heat is absorbed. From this, we can deduce that___
A hydrogen and iodine react more rapidly at lower temperature
B the energy involved in making the bonds is less than that involved in breaking the bonds.
C more bonds are broken than formed
D the formation of H-I bonds uses up energy.
Correct answer is B. Since overall, heat is absorbed, means is endothermic reaction means energy taken in during bond breaking exceeds energy given out during bond forming. For option C, you need to draw the Kekule structures of the reactants, intermediates and products, to compare and deduce (in addition, all bonds need to be covalent bonds for a straightfoward comparison, which in this particular reaction they are indeed).
>>> State the type of energy change that takes place when anhydrous sodium carbonate dissolves in water. Initial temperature of water was 25deg cel. after dissolving in water, temperature of solution is 34deg cel, an increase by 9deg cel. <<<
This is an exothermic reaction, since overall (ie. net change), heat energy was given to the environment (ie. the solution, and the thermometer).
Remember the best example of an EXOthermic reaction (in which heat EXits; in contrast to heat ENtering in an ENdothermic reaction), is that of combustion (aka burning), and your hand serves as the environment and thermometer. Your hand feels hot, so it's an exothermic reaction (since heat is transferred from the reactants/reaction to the environment which is your hand).
Can you please explain to me the first question again? I don't kind of understnad. But doesn't burning GIVE OUT heat to surrounding too?
And the environment in question 3 is referring to the solution or the atmosphere around? Since the temperature of solution increases, heat is taken in by the solution? So shouldn't it be an endothermic reaction? Thankyou
Q1.
energy released in terms of heat is = bond energy
so if i release more energy when i form a compound (highly exothermic) => the bond energy is gampua strong => it will be super hard to decompose the compound by heat..
Q3.
solution increase by 9 degree => your environment gain energy => dissolving the thing is exothermic. heat is GIVEN OUT by the dissolving of salt so is exothermic.
your viewpoint is reversed
your explanation is "HEAT ENERGY is taken IN by solution (by that i assume you mean heat energy GAIN by solution)"
but endothermic means that the COMPOUND "takes in" heat energy to form its bonds, MEANING that your solution will have heat energy LOSS, nt gain
When a reaction is endothermic, the reaction takes in more energy (during bond breaking) than it gives out (during bond forming), hence the environment which includes the solution as well as the thermometer as well as your hand (if you're holding the beaker, for instance) becomes or feels colder. Eg. from 37 deg C to 27 deg C.
When a reaction is exothermic, the reaction gives out more energy (during bond forming) than it takes in (during bond breaking), hence the environment which includes the solution as well as the thermometer as well as your hand (if you're holding the beaker, for instance) becomes or feels warmer. Eg. from 37 deg C to 47 deg C.
bonkysleuth, Your confusion here is that you think reactants = solution, which is incorrect. By definition, solution = solute (minority) dissolved in solvent (majority). And the majority of the solution is, by definition, the solvent, which is the also environment for the reaction (together with the thermometer, your hand, etc).
Again, note that :
Endothermic = your hand (or thermometer) feels cold.
Exothermic = your hand (or thermometer) feels hot.