Heat reactions (1 Viewer)

[Pepperpie]

Hi I got stuck on the following questions and I don't know how they are done;

Write the chemical equation and calculate delta H for the reaction or process which occurs in each of the following;

a) when 1.5g sulfur is burned in air (oxygen) 13.9kj of heat is released
b) 4.1 kj heat is required to decompose 2.3g calcium carbonate to calcium oxide and carbon dioxide
c) when 5.0g sodium hydroxide in solution reacts with excess hydrochloric acid solution, 6.9 kj of heat is released

a) Zn(s) + Br2(l) => ZnBr2 delta H =-329 kj/mol
4.3 g zinc reacts with excess bromine
b) Pcl5 => PCl3 + Cl2 delta H = +93 kj/mol
18.2g phosphorus pentachloride is decomposed
c) Na2S2O3.5H2O => Na2S2O3 delta H = +45 kj/mol
46.0 g sodium thiosulfate pentahydrate is dissolved in water

For reaction
2NO +O2 => 2NO2 delta H = -114 kj mol

Calculate delta H for
2NO2 => 2NO +O2

Thanks in advance if you can help out!!

 

[Kurosaki]

Hi I got stuck on the following questions and I don't know how they are done;

Write the chemical equation and calculate delta H for the reaction or process which occurs in each of the following;

a) when 1.5g sulfur is burned in air (oxygen) 13.9kj of heat is released
b) 4.1 kj heat is required to decompose 2.3g calcium carbonate to calcium oxide and carbon dioxide
c) when 5.0g sodium hydroxide in solution reacts with excess hydrochloric acid solution, 6.9 kj of heat is released

a) Zn(s) + Br2(l) => ZnBr2 delta H =-329 kj/mol
4.3 g zinc reacts with excess bromine
b) Pcl5 => PCl3 + Cl2 delta H = +93 kj/mol
18.2g phosphorus pentachloride is decomposed
c) Na2S2O3.5H2O => Na2S2O3 delta H = +45 kj/mol
46.0 g sodium thiosulfate pentahydrate is dissolved in water

For reaction
2NO +O2 => 2NO2 delta H = -114 kj mol

Calculate delta H for
2NO2 => 2NO +O2

Thanks in advance if you can help out!!

Hello, when you do these questions you like to see whether energy is released or absorbed.
Released- negative enthalpy
Absorbed- positive enthalpy.

So e.g. for a), you have n(s)=1.5/32.07. You use that number to divide the energy involved which is 13900 J, and then write the answer as negative, since energy is released. Writing like, x J/mol Sulfur

 

[someth1ng]

Write the chemical equation and calculate delta H for the reaction or process which occurs in each of the following;

a) when 1.5g sulfur is burned in air (oxygen) 13.9kj of heat is released
b) 4.1 kj heat is required to decompose 2.3g calcium carbonate to calcium oxide and carbon dioxide
c) when 5.0g sodium hydroxide in solution reacts with excess hydrochloric acid solution, 6.9 kj of heat is released

I'll do the first one so you can see the working.

So burning of sulfur is just:
S(s)+O2(g)-->SO2(g)

Now, you know that 13.9kJ is released per 1.5g of sulfur, yes?
That means -9.27kJ/g

All you need to do is:
deltaH=E/m * m/M
deltaH=-9.27kJ/g * 32 g/mol
deltaH=-296.53 kJ/mol

 

[Pepperpie]

Hello, when you do these questions you like to see whether energy is released or absorbed.
Released- negative enthalpy
Absorbed- positive enthalpy.

So e.g. for a), you have n(s)=1.5/32.07. You use that number to divide the energy involved which is 13900 J, and then write the answer as negative, since energy is released. Writing like, x J/mol Sulfur

Where does 32.07 come from?

 

[someth1ng]

Where does 32.07 come from?

Molar mass of sulfur.

 

[Streetboy]

Pepperpie here is all site with all the chemical questions for yeally 11, all in one.

make sure you know all the type of equations and how to balanced them out, after that learn all your formula's and how to apply them, by simply buying a book and list all the formula's and most most importantly, when ever you can't do a problem write it out, because in order for to maximise your Atar, you have to know every single dotpoint + your HSC content well enough so when you see a question you can say, yeah I did this one day. this is the only study method that will get you far, if you only rely on people to do your questions, they want do you HSC, will they?

plus, you need to start getting ready, if you really serious about HSC, here a site: CHEMICAL REACTIONS IN YEAR 11 get start ortherwise ( you will fail your HSC, if you can't do simply calculations).

METALS IN WATER

Reactive Metal + Liquid Water → Metal Hydroxide + Hydrogen Gas

E.g. Na(s) + H2O(l) → NaOH(aq) + H2(g)

Metal + Steam → Metal Oxide + Hydrogen Gas

E.g. Zn(s) + H2O(g) → ZnO(s) + H2(g)



COMBUSTION OF A METAL

Metal + Oxygen Gas → Metal Oxide

E.g. 2Mg(s) + O2(g) → MgO(s)



COMBUSTION OF A CARBON COMPOUND

Hydrocarbon + Oxygen → Carbon Dioxide Gas + Liquid Water

E.g. 2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(l)



METALS WITH ACIDS

Metal + Acid → Salt + Hydrogen gas

E.G. Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)



CARBONATES WITH ACIDS

Carbonate + Acid → Salt + Carbon Dioxide Gas + Liquid Water

E.g. Na2CO3(aq) + 2HCl(aq) → 2NaCl(aq) + CO2(g) + H2O(l)



OXIDATION

Metal → Metal Ion + Electron/s

E.g. Cu(s) → Cu2+(aq) + 2e-



REDUCTION

Metal Ion + Electron/s → Metal

E.g. Ag+(aq) + e- → Ag(s)



REDOX (REDUCTION-OXIDATION REACTIONS)

This reaction involves the transfer of electron/s from one reactant to another. This thus results in both a reduction and oxidation reaction occurring. To obtain the redox reaction, you can either write the net ionic equation for a displacement reaction (option 1) or add reduction and oxidation reactions together (option 2).

E.g. OPTION 1:

Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq) + 2Ag(s)

Cu(s) + 2Ag+(aq) + 2NO3- → Cu2+(aq) + 2NO3- + 2Ag(s)

Cu(s) + 2Ag+(aq) + 2NO3- → Cu2+(aq) + 2NO3- + 2Ag(s)

Cu(s) + 2Ag+(aq) → Cu2+(aq) + 2Ag(s)



E.g. OPTION 2

NOTE: BOTH THE CONSERVATION OF MASS AND CHARGE MUST BE SHOWN IN YOUR EQUATION!

Cu(s) → Cu2+(aq) + 2e-

+

2Ag+(aq) + 2e- → 2Ag(s)

__________________

Cu(s) + 2Ag+(aq) + 2e- → Cu2+(aq) + 2e- + 2Ag(s)

Cu(s) + 2Ag+(aq) + 2e- → Cu2+(aq) + 2e- + 2Ag(s)

Cu(s) + 2Ag+(aq) → Cu2+(aq) + 2Ag(s)



PHOTOSYNTHESIS

Carbon Dioxide Gas + Liquid Water → Solid Glucose + Oxygen Gas

I.e. 6CO2(g) + 6H2O(l) → C6H12O6(s) + 6O2(g)



RESPIRATION

Aqueous Glucose + Oxygen Gas → Carbon Dioxide Gas + Liquid Water

I.e. C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(l)



LIME WATER TEST (LIME WATER AND CARBON DIOXIDE)

Calcium hydroxide + Gaseous carbon dioxide → Solid calcium carbonate + liquid water

I.e. Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)

here is all you need for chemistry year 11, let m e know if you also need the year 12, you can search on on matrix education on Google. ( credit oes to matrix education for there wonderful site! helping thousands of students)

here is the formula you will ever need your year 11 ( I repeat this follows for yar 12, so learn them well know to make your self easily in year 12).

n=m/Mm'

n= v/Mv

here is another site showing you balancing chemical equations! www.youtube.com/watch?v=lFIbPlgDREI

another one from talent 100 tutor ( he is good, goes through the steps of chemical calaltions, lol) www.youtube.com/watch?v=_rPUuUBt_zk:


good luck, study hard you will succeed, when ever you don't understand something, seek help immedielt you don't want to go in the exam and say if only I did this then I would have gotten full marks,

three steps for every year 11 students, no matter what the course/subject is

understand, apply, practice quetsions ( especially for chem/bio/physics, maths)

 

[Pepperpie]

Pepperpie here is all site with all the chemical questions for yeally 11, all in one.

make sure you know all the type of equations and how to balanced them out, after that learn all your formula's and how to apply them, by simply buying a book and list all the formula's and most most importantly, when ever you can't do a problem write it out, because in order for to maximise your Atar, you have to know every single dotpoint + your HSC content well enough so when you see a question you can say, yeah I did this one day. this is the only study method that will get you far, if you only rely on people to do your questions, they want do you HSC, will they?

plus, you need to start getting ready, if you really serious about HSC, here a site: CHEMICAL REACTIONS IN YEAR 11 get start ortherwise ( you will fail your HSC, if you can't do simply calculations).

METALS IN WATER

Reactive Metal + Liquid Water → Metal Hydroxide + Hydrogen Gas

E.g. Na(s) + H2O(l) → NaOH(aq) + H2(g)

Metal + Steam → Metal Oxide + Hydrogen Gas

E.g. Zn(s) + H2O(g) → ZnO(s) + H2(g)



COMBUSTION OF A METAL

Metal + Oxygen Gas → Metal Oxide

E.g. 2Mg(s) + O2(g) → MgO(s)



COMBUSTION OF A CARBON COMPOUND

Hydrocarbon + Oxygen → Carbon Dioxide Gas + Liquid Water

E.g. 2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(l)



METALS WITH ACIDS

Metal + Acid → Salt + Hydrogen gas

E.G. Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)



CARBONATES WITH ACIDS

Carbonate + Acid → Salt + Carbon Dioxide Gas + Liquid Water

E.g. Na2CO3(aq) + 2HCl(aq) → 2NaCl(aq) + CO2(g) + H2O(l)



OXIDATION

Metal → Metal Ion + Electron/s

E.g. Cu(s) → Cu2+(aq) + 2e-



REDUCTION

Metal Ion + Electron/s → Metal

E.g. Ag+(aq) + e- → Ag(s)



REDOX (REDUCTION-OXIDATION REACTIONS)

This reaction involves the transfer of electron/s from one reactant to another. This thus results in both a reduction and oxidation reaction occurring. To obtain the redox reaction, you can either write the net ionic equation for a displacement reaction (option 1) or add reduction and oxidation reactions together (option 2).

E.g. OPTION 1:

Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq) + 2Ag(s)

Cu(s) + 2Ag+(aq) + 2NO3- → Cu2+(aq) + 2NO3- + 2Ag(s)

Cu(s) + 2Ag+(aq) + 2NO3- → Cu2+(aq) + 2NO3- + 2Ag(s)

Cu(s) + 2Ag+(aq) → Cu2+(aq) + 2Ag(s)



E.g. OPTION 2

NOTE: BOTH THE CONSERVATION OF MASS AND CHARGE MUST BE SHOWN IN YOUR EQUATION!

Cu(s) → Cu2+(aq) + 2e-

+

2Ag+(aq) + 2e- → 2Ag(s)

__________________

Cu(s) + 2Ag+(aq) + 2e- → Cu2+(aq) + 2e- + 2Ag(s)

Cu(s) + 2Ag+(aq) + 2e- → Cu2+(aq) + 2e- + 2Ag(s)

Cu(s) + 2Ag+(aq) → Cu2+(aq) + 2Ag(s)



PHOTOSYNTHESIS

Carbon Dioxide Gas + Liquid Water → Solid Glucose + Oxygen Gas

I.e. 6CO2(g) + 6H2O(l) → C6H12O6(s) + 6O2(g)



RESPIRATION

Aqueous Glucose + Oxygen Gas → Carbon Dioxide Gas + Liquid Water

I.e. C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(l)



LIME WATER TEST (LIME WATER AND CARBON DIOXIDE)

Calcium hydroxide + Gaseous carbon dioxide → Solid calcium carbonate + liquid water

I.e. Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)

here is all you need for chemistry year 11, let m e know if you also need the year 12, you can search on on matrix education on Google. ( credit oes to matrix education for there wonderful site! helping thousands of students)

here is the formula you will ever need your year 11 ( I repeat this follows for yar 12, so learn them well know to make your self easily in year 12).

n=m/Mm'

n= v/Mv

here is another site showing you balancing chemical equations! www.youtube.com/watch?v=lFIbPlgDREI

another one from talent 100 tutor ( he is good, goes through the steps of chemical calaltions, lol) www.youtube.com/watch?v=_rPUuUBt_zk:


good luck, study hard you will succeed, when ever you don't understand something, seek help immedielt you don't want to go in the exam and say if only I did this then I would have gotten full marks,

three steps for every year 11 students, no matter what the course/subject is

understand, apply, practice quetsions ( especially for chem/bio/physics, maths)

Thank you so much this really helped