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OCR Salters B - Chemistry of Natural Resources June 2010 (post discussion)

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I understand what u do for a reflux but i dont understand why you do it, surely by letting the distilled product back into the pear-shaped flask nothing is happening. Does that make sense? How are the reactants and products different?

Reply 81

RKShereni

HollyJ16

In terms of distillation;
Its the stuff that enters the condenser, that gets cooled by water and liquefies. Then it comes out the other end !

You should know what the boiling point of you product you want to collect is, then you know that when youve heated it to a certain point, what comes out the other end, is your product.

The stuff that falls back into the flask will vapourise when it hits its boiling point. So in theory if you continue to heat your reactants, then they should all become products.

Make any sense?

Also have you tried looking in the back of the Ideas book for the method? It might help your understanding :smile:

Reply 82

HollyJ16

ohhh okie dokie, thanks :smile:

Reply 83

username279062

aj.x

heya guys, just a few questions...

as there isn't many new spec papers, i've been doing old ones, and i was just wondering if we need to know about the following:

1. froth flotation
2. vacuum filteration

[\QUOTE]
No we don't, that was only on the old spec :smile:

Reply 84

beckyxo

I dunno if this sounds stupid... but what does 'baked out of the rocks' actually mean? why baked? :/

Reply 85

RKShereni

beckyxo

I dunno if this sounds stupid... but what does 'baked out of the rocks' actually mean? why baked? :/

Becauseee the atmopshere is very hot, so it sort of gets evaporated out...well thats my understanding of it anyway :smile:

Reply 86

tomio

can some help me with this deutrium to hydrogen ratio idea. Why does high ration on venus mean that there was once water? i dooooooont get it.

Reply 87

tomio

Can some help me with this deutrium hydrogen ration consept? i just dont get why high ratio on venus means there was once water.

Reply 88

Confusing_Chem

What a bloody help! Thanks for this. I'm pulling an all nighter just to study it all.

I don't find any of Chemistry hard or confusing, I just forget...and when I forget I TRY to make sense of things and I end up muddling it all up and confusing myself.

Hence the 'Confusing Chem' nick...should've been more like 'Confusing_Myself' ¬¬

Reply 89

hahahah

does anyone know what an amine group thing is? :s-smilie:

Reply 90

spring_bee040906

hahahah

does anyone know what an amine group thing is? :s-smilie:

halogenoalkanes react with ammonia to form the homologous series 'amines'

:smile:

good luck all!

Reply 91

Slowbro93

Was there an experiment for amine, cant remember doing one

Reply 92

beckyxo

Thank you! :smile:

This thread is a life saver haha :smile:

Reply 93

kutchinder

answers to thsoe questions please?

Reply 94

beckyxo

oh and heres some questions my chem teach put up for us,
some of them have answers but not all

Suggestions for pre-release material questions

What is photochemical dissociation?
The break up of molecules by UV light in the atmosphere
How was our current atmosphere formed? As our differentiated core created a magnetic field around the earth, heavier elements were retained by our atmosphere, this combined with an increase in life specifically cyanobacteria and plants led to a reduction of nitrogen and other elements useful to growth, and an increase in oxygen and oxides.
In Photosynthesis if you had 8.8g of CO2 how many grams of Glucose would you obtain.
CO2 = (1x12) + (2x16) = 44 , C6H12O6 = (6 x 12) + (12 x 1) + (6 x 16) = 180
8.8 / (6 x 44) = 1/30 , 1/30 x 180 = 6 so 6g of glucose obtained.
Where is 97% of the atmosphere?

97% of the atmosphere lies within 30km of the earth's surface

Explain how the oxygen levels have reached the steady state of today?
Steady state means that there is an equal amount of oxygen being produced as there is being used. Therefore if the oxygen consumtion is increased due to chemical weathering, animal respiration and burning fossil fuels, more oxygen is needed to be produced through photosynthesis and photochemical dissociation.
Q - State the main ways which cause oxygen levels to rise and fall.

.
A - There are two main ways in which oxygen levels have risen, this is by Photochemical Dissociation and Photosynthesis. The three ways which cause oxygen levels to decrease are Chemical Weathering, Animal Respiration and Burning Fossil Fuels
Compare the Earths first atmosphere to the current atmosphere of the Earth, and explain what has caused this difference. The Earths early atmosphere would have been mostly hydrogen and helium. The composition of the current atmosphere is very different, it includes small amounts of hydrogen and helium with mostly nitrogen (78%) oxygen (21%) and Argon (1%). This change occurred because of chemical reactions such as Photosynthesis (6CO2 +- 6H2O -> 6O2 + C6H12O6) adding oxygen to the atmosphere and the differentiation of the core of the Earth allowing heavier gases to be retained. Other organisms such as cynobacteria (green-blue algae) also released oxygen into the atmosphere during the Proterozoic era.
Calculation. Give the constituent Carbon Dioxide in ppm when in dry, unpolluted tropospheric air.
0.0314% X 10,000 = 314ppm
Easy: How does the existance of red beds suggest increasing oxygen levels in the atmosphere? Red beds contain lots of highly oxidised iron in the form of hematite (Fe2O3) which has only become common in the last 540million years and is never found longer than 2.3billion years ago. This suggests that 2.3billion years ago there was very little oxygen in the atmosphere and until 540million years it it has been slowly increasing and after this it has become common place. This is because oxygen is needed in order to oxidise the iron to form hematite, meaning hematite can only be formed when oxygen levels are high, and because more has formed recently than before it suggests that oxygen levels have increased.

Difficult: Describe how temperature changes with altitude?

Within the troposphere temperature decreases with altitude which is known as the environmental lapse rate and is roughly equal to -6.5oC per kilometre. Altitude continues increasing until the tropopause where the temperature doesn't change at all. In the stratosphere temperature increases with altitude, photodissociation occurs in this section of the atmopshere. These reactions release heat energy causing the air to warm up, then warm air then rises to the top leaving cooler more dense air at the bottom.

. The earth's early composition probably consisted mainly of two gases, what were these and why were they lost?

Suggest why and how the interaction of ultraviolet light with ozone causes an increase in temperature.

Using table 1 convert each percentage by volume value into a value of parts per million
Convert 18.18ppm to a percentage 18.19/10000 =0.001818%

How does photochemical dissociation release oxygen into the atmosphere? The UV light from the sun breaks the bonds in the water molecules which creates hydoxyl and hydrogen radicals. Hydroxyl radicals can split again to produce oxygen radicals which eventually form oxygen molecules

Why does the temperature in the atmosphere change between the tropsphere and the stratosphere?

The concentration of ozone is higher in the stratosphere after the tropopause and the interactions between UV light and the ozone cause the increase in temperature.

Easy Question
What was almost all of Earth's first atmosphere made up of?? Answer
Hydrogen and Helium.
Medium Question
What are the main contributers to oxygen in the atmosphere today Answer
Photochemical dissociation and Photosynthesis.
Hard Question
Explain how rocks can be used as evidence for the build up of oxygen over time.

Answer
Rock records show that rocks that have not been in contact with the atmosphere for a long time have less oxygen in them that rocks that have been in contact with the atmosphere more recently. This tells us that there was less oxygen in the atmosphere when these rocks were in contact with it.

And others without the answers
Where does the dense part of the atmosphere lie?

How much Hydrogen is in the air (in parts per million) ?

What is meant by the weathering process?

What happened to the Hydrogen and Helium?

How much free oxygen is there today?

Name one process that causes oxygen production? Explain it

Name a process that consumes oxygen?Explain it

What is Banded Iron Formation (BIF)?

What is the minimum age of a rock with a red bed?

What has happened to the amount of oxygen over time?

How many collisions per second near sea level?

Calculate 78.084% in parts per million

Calculate 18.18 parts per million as a percentage

What is an environmental lapse rate

In the bottom layer, what does the temperature do with altitude?

What is the top of the troposphere marked by?

In the stratosphere, what happens to temperature with height?

What does ozone – ultra violet interaction cause?

Reply 95

aj.x

beckyxo

oh and heres some questions my chem teach put up for us,
some of them have answers but not all....

thank you so much :smile:

x x x

Reply 96

Saphire1

beckyxo

I dunno if this sounds stupid... but what does 'baked out of the rocks' actually mean? why baked? :/

Not stupid, you're genius coz this came up :yep:

Reply 97

Slowbro93

Saphire1

Not stupid, you're genius coz this came up :yep:

happy that came up, how did you find the 6 mark question on mars

Reply 98

Saphire1

cpdavis

happy that came up, how did you find the 6 mark question on mars

Thought that was okay, I put something along the lines of mars being far away from the sun and water freezing, CO2 staying in the rocks/freezing and because water vapour is a greenhouse gas and they are reducing, IR radiation is not absorbed (goes into space) so temperature decreases (think ive just written that)

because earth is not too far away/close it has the right temp for liquid water and life puts CO2 in the atmosphere by respiration

i think it was something like that anyway :smile: