last minute SNS Questions!!!!!!

[HC_smiles]

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Here are some questions from Barrons SNS that I needed some help to. I'm taking the DAT on Friday so any help would be great!!! 👍

1) Assuming independent assortment, the possible number of different gamete types from 3 homologous pairs is: ANSWER = 8

2) Diffusion rate of methane gas compared to that of helium is: ANSWER = half as fast

3) Which ion is isoelectronic with Ba2+? ANSWER = Xe

4) What is the mass, in grams, of 245 mL of SO2 at STP? ANSWER = 0.694

5) If 14 g of NaF are dissolved in 400 mg H2O, what is the molality of the solution? ANSWER = 0.83 m

6) How much 4 M Ca(OH)2 is needed to neutralize 300 mL of 3M HNO3? ANS = 112.5 mL

7) How many atoms of carbon are in 4.00 x 10-8 g of C3H8? ANS = 4.00 x 10^4

8) If all of the chloride in a 5.0 g sample of an unknown metal chloride is precipitated as AgCl with 70.9 mL of 0.201 M AgNO3, what is the percentage of chloride in the sample? ANSWER NOT GIVEN!!!!!

**General Question:
What exactly do catalysts do??? According to the answer, it increases free energy. I thought they also increase the rate at which the product is formed???? Or is that like enzymes and lowering Ea???

 

[dat_student]

...

**General Question:
What exactly do catalysts do??? According to the answer, it increases free energy. I thought they also increase the rate at which the product is formed???? Or is that like enzymes and lowering Ea???

Catalysts work by changing the activation energy for a reaction, i.e., the minimum energy needed for the reaction to occur. This is accomplished by providing a new mechanism or reaction path through which the reaction can proceed. When the new reaction path has a lower activation energy, the reaction rate is increased and the reaction is said to be catalyzed. NOTE: Catalysts are not consumed in the process

 

[RockstarDMD]

Here are some questions from Barrons SNS that I needed some help to. I'm taking the DAT on Friday so any help would be great!!! 👍

1) Assuming independent assortment, the possible number of different gamete types from 3 homologous pairs is: ANSWER = 8

2^n =2^3

4) What is the mass, in grams, of 245 mL of SO2 at STP? ANSWER = 0.694

(245ml)(1L/1000mL)(1mole/22.4L)(64g/1mole) = 0.694

5) If 14 g of NaF are dissolved in 400 mg H2O, what is the molality of the solution? ANSWER = 0.83 m

I think you were meaning g not mg?
(14g)(1mole/42g) =.33
(.33mol)/(.4kg) = .83

6) How much 4 M Ca(OH)2 is needed to neutralize 300 mL of 3M HNO3? ANS = 112.5 mL

Use Normality here. NaVa=NbNb

(3M)(300mL)/(8M) = 112.5

 

[HC_smiles]

Here are some questions from Barrons SNS that I needed some help to. I'm taking the DAT on Friday so any help would be great!!! 👍


2^n =2^3



(245ml)(1L/1000mL)(1mole/22.4L)(64g/1mole) = 0.694



I think you were meaning g not mg?
(14g)(1mole/42g) =.33
(.33mol)/(.4kg) = .83



Use Normality here. NaVa=NbNb

(3M)(300mL)/(8M) = 112.5

Thats the part i got confused on....it definitely says mg...thanx for all ur help everyone! 😍

 

[HC_smiles]

Here are some questions from Barrons SNS that I needed some help to. I'm taking the DAT on Friday so any help would be great!!! 👍

1) Assuming independent assortment, the possible number of different gamete types from 3 homologous pairs is: ANSWER = 8

2) Diffusion rate of methane gas compared to that of helium is: ANSWER = half as fast

3) Which ion is isoelectronic with Ba2+? ANSWER = Xe

4) What is the mass, in grams, of 245 mL of SO2 at STP? ANSWER = 0.694

5) If 14 g of NaF are dissolved in 400 mg H2O, what is the molality of the solution? ANSWER = 0.83 m

6) How much 4 M Ca(OH)2 is needed to neutralize 300 mL of 3M HNO3? ANS = 112.5 mL

7) How many atoms of carbon are in 4.00 x 10-8 g of C3H8? ANS = 4.00 x 10^4

8) If all of the chloride in a 5.0 g sample of an unknown metal chloride is precipitated as AgCl with 70.9 mL of 0.201 M AgNO3, what is the percentage of chloride in the sample? ANSWER NOT GIVEN!!!!!

**General Question:
What exactly do catalysts do??? According to the answer, it increases free energy. I thought they also increase the rate at which the product is formed???? Or is that like enzymes and lowering Ea???

Hi again,

Thanx to dat and rockstar for helping me out on some of the questions. i was able to get some more so if any one could explain 3, 7, and 8 that would be awesome! 🙄

 

[RockstarDMD]

Hi again,

Thanx to dat and rockstar for helping me out on some of the questions. i was able to get some more so if any one could explain 3, 7, and 8 that would be awesome! 🙄

#3 Ba2+ is isoelectronic with Xe because the share the same electron configuration. [Kr]5s2 4d10 5p6

 

[lifeisgood]

Hi again,

Thanx to dat and rockstar for helping me out on some of the questions. i was able to get some more so if any one could explain 3, 7, and 8 that would be awesome! 🙄

#7 -- Take your mass (in g) divide it by the MW of propane MW(C3H8)=44 g/mol...that will give you # of moles. Then multiply by Avogadro's # 6.02 x 10>23 atoms/mole. Moles cancel and you are left w/ # of atoms.

#8 Find moles of Ag first by multiplying (0.201 mol/L)*(1L/1000mL)*(70.9mL) = 0.0143 mol Ag+

This is equal to mol Cl-. (0.0143 mol Cl-)*(35.45 g Cl-/mol Cl-) = 0.505 g Cl-

To find % in sample = (0.505 g Cl-)/(5.0 g sample)*100 = 10.1 % Cl- in sample.