You are Here: Home

# Help! Chem Synoptic Questions watch

1. God I'm so confused

Can anyone help me with these synoptic questions? I'd really appreciate it!

Q. The number of monochloro derivatives of CH3CH(CH3)CH3 is 1,2,3,4,5...what is monochloro derivatives? I don't get it..

Q. The equilibrium constant for the following reaction is 4 at a given temperature.

2HI(g) ---> H(2) g + I(2) g

When a sample of HI is decomposed in a sealed tube at this temperature the equilibrium concentration of HI is 0.2 mol/l . The equilibrium conc (in mol/l) of hydrogen in this tube is: 0.1,0.2,0.4,0.8,0.16 ...I got [H(2)][I(2)] = 0.16 but how do I find [H(2)] then?

Q. The equation for the direct reaction between Hydrogen and oxygen is

2H(2) + O(2) --> 2H(2)O delta H = -484 kJ/mol

Which one of the following is NOT true concerning a platinum catalyst for this reaction?

It speeds up the reaction
Remains chemically unchanged at the end
Lowers the value of delta H
Provides alternative route for reaction
Provides surface on which the reactino can take place.

...aren't they all correct?

Q. A sample of pig iron contains 3.92% carbon by mass, the rest being iron. In 100 atoms in a sample of the pig irion, how many atoms would be carbon?

I get the C:Fe ratio to be 1:5.2 so can I round this to CFe(5)?
In doing this 100/6 = 16+2/3 but the answers give:

6,8,10,16 or 20 so I can round this to 16??
2. (Original post by Sugaray)
God I'm so confused

Can anyone help me with these synoptic questions? I'd really appreciate it!

Q. The number of monochloro derivatives of CH3CH(CH3)CH3 is 1,2,3,4,5...what is monochloro derivatives? I don't get it..

Q. The equilibrium constant for the following reaction is 4 at a given temperature.

2HI(g) ---> H(2) g + I(2) g

When a sample of HI is decomposed in a sealed tube at this temperature the equilibrium concentration of HI is 0.2 mol/l . The equilibrium conc (in mol/l) of hydrogen in this tube is: 0.1,0.2,0.4,0.8,0.16 ...I got [H(2)][I(2)] = 0.16 but how do I find [H(2)] then?

Q. The equation for the direct reaction between Hydrogen and oxygen is

2H(2) + O(2) --> 2H(2)O delta H = -484 kJ/mol

Which one of the following is NOT true concerning a platinum catalyst for this reaction?

It speeds up the reaction
Remains chemically unchanged at the end
Lowers the value of delta H
Provides alternative route for reaction
Provides surface on which the reactino can take place.

...aren't they all correct?

Q. A sample of pig iron contains 3.92% carbon by mass, the rest being iron. In 100 atoms in a sample of the pig irion, how many atoms would be carbon?

I get the C:Fe ratio to be 1:5.2 so can I round this to CFe(5)?
In doing this 100/6 = 16+2/3 but the answers give:

6,8,10,16 or 20 so I can round this to 16??

monochloro derivatives are hydrocarbons with one chlorine atom, i.e. the answer is 2.

in the second question you have [H2][I2] = 0.16 therefore to get [H2] you simply square root it (as H2 and I2 are present in a 1:1 molar ratio). Therefore the answer is 0.4.

In the third one, the third statement is untrue. a catalyst does not alter the delta H value of the reaction.

and in the last one the answer is 15.9944, which rounds up to 16.
3. (Original post by Sugaray)
Q. The equilibrium constant for the following reaction is 4 at a given temperature.

2HI(g) ---> H(2) g + I(2) g

When a sample of HI is decomposed in a sealed tube at this temperature the equilibrium concentration of HI is 0.2 mol/l . The equilibrium conc (in mol/l) of hydrogen in this tube is: 0.1,0.2,0.4,0.8,0.16 ...I got [H(2)][I(2)] = 0.16 but how do I find [H(2)] then?
[H(2)]= [I(2)] since they are both produced in equimolar amountsby the dissociation and there is none of them originally.

(Original post by Sugaray)
Q. The equation for the direct reaction between Hydrogen and oxygen is

2H(2) + O(2) --> 2H(2)O delta H = -484 kJ/mol

Which one of the following is NOT true concerning a platinum catalyst for this reaction?

It speeds up the reaction
Remains chemically unchanged at the end
Lowers the value of delta H
Provides alternative route for reaction
Provides surface on which the reactino can take place.

...aren't they all correct?
Lowers the value of delta H - Hess's Law states that the enthalpy change is independant of the route taken, and that includes catalysis.

(Original post by Sugaray)
Q. A sample of pig iron contains 3.92% carbon by mass, the rest being iron. In 100 atoms in a sample of the pig irion, how many atoms would be carbon?

I get the C:Fe ratio to be 1:5.2 so can I round this to CFe(5)?
In doing this 100/6 = 16+2/3 but the answers give:

6,8,10,16 or 20 so I can round this to 16??
If you actually work out the proportion of carbon atoms by dividing 1 by 5.2, and then times this by 100 to get the actual number, you do get 16. The rounding is not needed- in fact it just screws it up.

Hope this helps.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: April 19, 2004
Today on TSR

### University open days

1. University of Cambridge
Wed, 26 Sep '18
2. Norwich University of the Arts
Fri, 28 Sep '18
3. Edge Hill University
Faculty of Health and Social Care Undergraduate
Sat, 29 Sep '18
Poll

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE