need help with these gen chem questions

[jvss123]

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Question 1:
A regularly shaped object with a mass of 497g is weighed in H20. If the object had a volume of 184cm3, its apparent mass would be?
a) 21.10 g
b) 184g
c) 313 g
d) 497g
e) 681g

Question 2:
In a cylinder with N, which is insoluble in H20, there is a small amount of H20 at 25 degrees celcius. At this temperature H20 has a vapor pressure of 24 mmHg. If a piston were pushed into cylinder reducing volume to 1/2, partial pressure of gas would rise to:
a) 2 atm
b) 1200 mmHg
c) 1176 mmHg
d) 48 mmHg
e) 24 mmHg

Question 3:
Half-life of fermium 253/100 is 4.5 days. After a lapse of 13.5 days the fraction of a mole of fermium remaining would be:
a) 1/13.5
b) 1/8
c) 3/4.5
d) 3x(253/100)
e) 1/3

ANSWERS--> C, C and B

Unfortunately, there were no solution explanations and I just dont understand how to get the answers...please help... i really appreciate it 🙂

 

[JBarr29]

1) Apparent Weight =weight Of Water- Upward Thrust
so its just 497 - volume of the water or 184

so 497 - 184 = 313


3) In 13.5 days, fermium will undergo 3 half-lifes.
So say you start with 100g of fermium, in 4.5 days you will have 50 grams left. In another 4.5 days or at day 9 you will have half of 50 or 25 grams left. And in another 4.5 days (day 13.5) you will have half of 25 grams, or 12.5
12.5/100 = 12.5% or 1/8

you can also say 3 half-lifes will be (1/2)*(1/2)*(1/2)

number 2 ill work on and get back to you. hope that helped a little

 

[jvss123]

thank u so much that helps 🙂

 

[Denty8]

10 character

 

[jvss123]

hey, yes the book is very different. nonetheless, it is good practice material.. i have come across few questions where I don't at all agree with their answers and some had typos... it was published in 1999 n i dont know if they have updated or not.. but like i said its good practice material... their PAT books are really good... i have taken the can dat before and i am retaking it in a few days (SO SCARED) loll