gchem q's

[MoooShuuu]

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In which of the follwing are the atoms arranged by increasing atomic size?

Be<Na<Mg
Be<Mg<Na
*I thought it would be the second one since atomic radius increasing R-L and down ... but the answer is the first one.

What is the mass in grams of 245 ml of SO2 at STP? * Blanking out completely.... ans .694

When asked how many mole of sulfur are in 1 mole As2S3? Is it just S3--3 moles? So for two moles of compound, there would be 6 moles S ? Seems too easy...

In an experiment, 3.4 g of a carbon oxygen containing compound was obtained in a test tube. the weight of oxygen was found to be .65 g. What was the percentage of carbon in the compound.

The ans is 1-(.65/3.4))(100) I thought it would be that, but without the 1- part. Where is that coming from?


When given a reaction, A + 2B--> 2C + D
and asked to find the rate law, assuming A and B are both first rate rxns...would the rate law be

k [C]2 [D]/ [A] 2 where the coeffficients are moved to exponents and are multiplied by the found rates? ^1x 2B??

thanks for the clarification!

 

[MoooShuuu]

2 [D]/ [A] 2 where the coeffficients are moved to exponents and are multiplied by the found rates? ^1x 2B??

thanks for the clarification!

I don't understand why this is the answer. I always thought that C and D are not in the rate law. The answer given looks to me like Keq or law of mass action rather than rate law. Am I losing my mind?

 

[Phloem01]

In which of the follwing are the atoms arranged by increasing atomic size?

Be<Na<Mg
Be<Mg<Na
*I thought it would be the second one since atomic radius increasing R-L and down ... but the answer is the first one.

What is the mass in grams of 245 ml of SO2 at STP? * Blanking out completely.... ans .694

When asked how many mole of sulfur are in 1 mole As2S3? Is it just S3--3 moles? So for two moles of compound, there would be 6 moles S ? Seems too easy...

In an experiment, 3.4 g of a carbon oxygen containing compound was obtained in a test tube. the weight of oxygen was found to be .65 g. What was the percentage of carbon in the compound.

The ans is 1-(.65/3.4))(100) I thought it would be that, but without the 1- part. Where is that coming from?


When given a reaction, A + 2B--> 2C + D
and asked to find the rate law, assuming A and B are both first rate rxns...would the rate law be

k [C]2 [D]/ [A] 2 where the coeffficients are moved to exponents and are multiplied by the found rates? ^1x 2B??

thanks for the clarification!

These are from Baron's aren't they??? For the S02 problem just use PV=nRT, so PV=(mass/molarmass)RT. STP conditions mean 273K and 1atm.

Therefore, Mass=(MM)PV/RT

hope that helps

 

[MoooShuuu]

Thanks Phloem



I just really don't understand why ( k [C]2 [D]/ [A] 2 )is the answer for the last problem about the rate law from this eq: A + 2B--> 2C + D

Shouldn't it be something like R=K[C]2 [D] ?😕

 

[HowAboutDAT]

In which of the follwing are the atoms arranged by increasing atomic size?

Be<Na<Mg
Be<Mg<Na
*I thought it would be the second one since atomic radius increasing R-L and down ... but the answer is the first one.

I definitely agree with you hopefully its just a mistake in the book... any other opinions?

 

[Frederico Albin]

Doesn't rate laws only involves reactants?

 

[mezz01]

1) yeah, the rate law should be =k[A]^2
since it only involves the initial concentrations of the reactants not the products.
2) atomic radius question should be: Be<Mg<Na
3) How many atoms of Carbon are in 4x10^-8g of C3H8? should be: 1.64x10^15
4)The catalyst question ...shouldn't it be to "lower the activation energy," not increase free energy?
5) I'm still not sure about the percentage of carbon question. my answer would've been without the 1-...