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# AS Chemistry homework help!? watch

1. I would be really grateful if anyone can help me answer any of the following questions

- Can you explain why the mass of aluminium in aluminium hydride is a lot greater than the mass of hydrogen, even though there are three hydrogen atoms to every one aluminium atom in the compound?

- How much uranium would you get from 1000g of uranium oxide?

- How many moles of ions are there in 117g of sodium chloride?

- How many moles of electrons are there in 24 125 coulombs?

- If 25g of calcium carbonate is heated, calculate the mass of calcium oxide produced and the volume of CO2 produced (measured at room temp and pressure).

- What mass of sulphur dioxide will be produced when 4g of sulphur is burnt in oxygen. What will be the volume of this gas at room temp and pressure?

- What volume of H2S will react with 20dm3 of SO2 at room temp and pressure and what mass of sulphur with be formed?

2. 1st one is because aluminium atoms are heavier (more neutrons etc.)
The others, you need to do mole calculations, which you would have done in GCSE.
3. 1) Aluminium has a Mr of 27 and Hydrogen's Mr is 1 so even with 3xH the Mr is less.

2) 1000g of UO2

So mass/mr gives mols of UO2 ..... 1000/270 = 3.7 Mols

mol x Mr = mass 3.7 x 238 = 880.6g of Uranium.

3) Na+ and Cl- are both ions, so mass/mr = mols 117/58.5 = 2 Mols

4) not a clue sorry.....

5) balanced equation = CaCO3 = CaO + CO2

Ratio of 1mol : 1mol

25/100 = .25

therefore .25 x 56 = 14g

CBA to do anymore but hope the ones ive done help, sorry if there are mistakes im doing it from memory and havent done any of these calculations in a while
4. - How many moles of electrons are there in 24 125 coulombs?

You need the Faraday constant to solve this; it is the magnitude of electric charge per mole of electrons and equals (approximately) 96,485 C per mol.

Charge of 1 mole of electrons = 96485 C
So if you have 24125 C then you have 24125/96485 = 0.250 moles

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