# 2009 ADA Test (#41 and #65)

Discussion in 'DAT Discussions' started by Delegate, Aug 1, 2011.

1. ### Delegate

Joined:
Mar 21, 2011
Messages:
3
0
Hi all,

This is for those who have been practicing with 2009 practice test. I'm having trouble with #41 and #65. Please help!

41) Exactly 492g of kerosene are required to fill a certain container. If the density of the kerosene was 0.820g/ml-1, and at the same temperature the density of mercury was 13.5g/ml-1, then what mass of mercury in grams, would be necessary to fill the container?

65)Consider the equilibrium rxn: 2NO(g) + O2 (g)-->2 NO2 (g), K = 2.0.
Which of the following is the correct value of K for the reaction :
NO2(g)--> NO(g) + 1/2O2(g)?

Thank you!

2. ### PooyaH 2+ Year Member

Joined:
Apr 24, 2008
Messages:
804
0
Status:
Pre-Dental
1. You need to get the volume of the container first, so since the density is .82g/ml and you have 492g of kerosene, then .82g/ml = 492g/ml, ml = 492/.82 = 600ml

Since you're filling up the same container, use the same volume to get the grams of Mercury: 13.5g/ml = g/600ml, g of Mercury = (13.5g/ml)(600ml) = 8100g of Mercury

2. Since the moles of reaction has been cut in half, the new K = square root of K, and since it is showing the reverse reaction, the K has to be 1/K. So if you put those two together, you'd have 1/sq rt of 2.

3. OP

### Delegate

Joined:
Mar 21, 2011
Messages:
3
0
Thank you, thank you!!

We’ve been on the Internet for over 20 years doing just one thing: providing career information for free or at cost. We do this because we believe that the health education process is too expensive and too competitive.

We believe that all students deserve the same access to high quality information. We believe that providing high quality career advice and information ensures that everyone, regardless of income or privilege, has a chance to achieve their dream of being a doctor.