sig fig rule on the DAT

[gangazi]

On the DAT, are we supposed to follow the sig fig rule? ie 6.75g - 4.6g = 2.2g or 2.15g?

I was doing DATqvault and picked 2.2g because of sig fig rule but apparently the answer is 2.15g

what to do on the real DAT?

Thank you

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[aj30]

Don't worry about it. On the DAT the answers will be far enough apart, sig figs are a non issue.

 

[rak173]

On the DAT, are we supposed to follow the sig fig rule? ie 6.75g - 4.6g = 2.2g or 2.15g?

I was doing DATqvault and picked 2.2g because of sig fig rule but apparently the answer is 2.15g

what to do on the real DAT?

Thank you

How is 2.15g correct answer here? I also think 2.2g follows the sig figs rule.

 

[Mrhyde]

How is 2.15g correct answer here? I also think 2.2g follows the sig figs rule.

For subtraction and addition you go with the least decimal places after the decimal

For Multiplication and Division you go with the least Sig Figs

--> So in this case it would be 2.2g since that follows the above rule
.....2.15 would Not be right

 

[gangazi]

Suggest an experiment that could distinguish a polar compound from a ionic compound.

• Observe if the compound is attracted to a magnet
• Attempt to dissolve the compound in a polar solvent
• Examine the compound with a microscope
• Correct Answer
  Attempt to run an electrical current through a solution of each compound
• Your Answer
  Determine the compound's melting point

I picked determine the compounds mp because ionic would have high mp/bp... and did not pick "attempt to run an electrical current" because I thought polar compounds could run an electrical current...
what do you guys think about this one?

 

[rak173]

I was doing DATqvault and picked 2.2g because of sig fig rule but apparently the answer is 2.15g

So is this question wrong in qvault?

 

[DAT Destroyer]

On the DAT, are we supposed to follow the sig fig rule? ie 6.75g - 4.6g = 2.2g or 2.15g?

I was doing DATqvault and picked 2.2g because of sig fig rule but apparently the answer is 2.15g

what to do on the real DAT?

Thank you

For most DAT questions, significant figures should not be an issue, but never let your guard down. You stand correct, when adding and subtracting you need to look at the number of digits after the decimal.

Hope this helps..

Dr. Romano

 

[Mrhyde]

Suggest an experiment that could distinguish a polar compound from a ionic compound.

• Observe if the compound is attracted to a magnet
• Attempt to dissolve the compound in a polar solvent
• Examine the compound with a microscope
• Correct Answer
  Attempt to run an electrical current through a solution of each compound
• Your Answer
  Determine the compound's melting point

I picked determine the compounds mp because ionic would have high mp/bp... and did not pick "attempt to run an electrical current" because I thought polar compounds could run an electrical current...
what do you guys think about this one?

Conductors are typically any material in which electrons are free to move about. liquid ionic compounds, as well as metals are generally considered good conductors. Most nonmetals are not good conductors... I don't thing polarity of a molecule has anything to do with its conductivity. It says "a solution" so I assume it was a liquid ionic compound which is why that would conduct electricity.

--- As far as melting point/boiling point ? I dont think that would help because perhaps its not considered an "absolute" that ALL ionic compounds have much higher mp and bp when compared to a polar compound. Maybe there are a few polar and ionic compounds that exist that are similar in range. So ionic compounds having high mp and bp is true and a good rule of thumb but maybe the other answer was just the "best" choice and this answer was not necessarily wrong but not the best

 

[Likkriue]

@gangazi I would also add an example to a Mrhydes post, glucose for example is extremely polar. But glucose does no disassociate at all when placed in water because there's no ionic bonds in glucose. Ionic compounds however does have ionic bonds, thus will react with an electrical current (by conducting it) when they are aqueous.
Also reacted to conductivity Ionic solids will not conduct electricity. This is a trick question that is very common, be careful.

 

[gangazi]

@gangazi I would also add an example to a Mrhydes post, glucose for example is extremely polar. But glucose does no disassociate at all when placed in water because there's no ionic bonds in glucose. Ionic compounds however does have ionic bonds, thus will react with an electrical current (by conducting it) when they are aqueous.
Also reacted to conductivity Ionic solids will not conduct electricity. This is a trick question that is very common, be careful.

Hmm okay! I Recall from kaplan quizzes that HCl is an example of polar covalent that could conduct electricity so I guess I will have to recheck if thats what it was really saying haha

 

[Likkriue]

Hmm okay! I Recall from kaplan quizzes that HCl is an example of polar covalent that could conduct electricity so I guess I will have to recheck if thats what it was really saying haha

HCL however disassociates completely into ions! So it definitely conducts electricity. The bonds are not ionic BUT it does form ions. So the book is correct. H+ and Cl-. Compound does not need to be ionic to disassociate into ions, but it has to be able to form ions when disassociated.

 

[gangazi]

HCL however disassociates completely into ions! So it definitely conducts electricity. The bonds are not ionic BUT it does form ions. So the book is correct. H+ and Cl-. Compound does not need to be ionic to disassociate into ions, but it has to be able to form ions when disassociated.

Great!! Looks like I dont need to get out of bed to check it out