4 multiple choice chemistry questions, answers would help.. thank you?

Question

1. Write an equation for the dissociation of the following ionic compound when it dissolved in water Al2(SO4)3.
A. Al2(SO4) 3 (s) --> Al2+(aq) + SO43-(aq)
B. Al2(SO4) 3 (s) --> 2Al (aq) + 3SO43-(aq)
C. Al2(SO4) 3 (s) --> Al3+(aq) + SO42-(aq)
D. Al2(SO4)3(s) --> 2Al3+(aq) + 3SO42(aq)

23. How many grams of strontium nitrate Sr( NO3)2 would you need to prepare 2.00 L of a 0.400M solution of strontium nitrate?
A. 125 g
B. 169 g
C. 210 g
D. 299 g

24. What mass of methanol, CH3OH, must be dissolved to make 1.50 L of a 0.675M solution?
A. 4.5 g
B. 13.8 g
C. 22.1 g
D. 32.4 g

25. What is the molarity of a solution that contains 17.2 g of lithium perchlorate, LiClO4, in 2250 mL of solution?
A. .00760M
B. .0719M
C. .815M
D. 1.2M

Answer 1

1. C

23. B

Atomic weights: Sr=87.6 N=14 O=3 Sr(NO3)2=211

Let the solution be called S. Let strontium nitrate be called SN

2.00LS x 0.400molSN/1LS x 211gSN/1molSN = 169g Sr(NO3)2

24. D

Let the solution be called S. Let methanol be called M.

Atomic weights: C=12 H=1 O=16 CH3OH=32

1.50LS x 0.675molM/1LS x 32gM/1molM = 32.4g methanol

25. B

Let the solution be called S. Let lithium perchlorate be called LP

Atomic weights: Li=6.9 Cl=35.5 O=16 LiClO4=106.4

17.2gLP/2250mLS x 1000mLS/1LS x 1molLP/106.4gLP = 0.0718

Answer 2

a million) C - a pos. ion loses a million or greater electrons 2) B is the closes answer warmth = 100g x 15C x 4.186 J/gC = 6279 J 3) D melting, boiling, sublimation all require capability to take place so as that they are endothermic. condensation is the different of vaporizing so it's going to be exothermic 4) D comparable formula as Q2: warmth = 50g x 30C x 4.186J/gC = 6279 or 6300J Bonus) C - while including numbers, the smallest place the respond could have is the area each and every of the numbers have in user-friendly so C is the sole selection that the 10th place is the final place they the two have in user-friendly, the different alternatives have the hundredth place in user-friendly and their solutions might all be 445.20 no longer basically 445.2.

Answer 3

1. D
- However i think 3SO4 3 should be 3SO4 3-

23.B
M-> molarity which is mol/L so:
1. (.400 mol/L)(2.0L)= .800mol --> liters are canceled
2. find how many grams are in one mol of Sr(NO3)2
Sr: 87.62g/mol
N: 14.0 g/mol
O: 16.0 g/mol

Sr(NO3)2: (87.62g/mol) + 2(14.0g/mol) + 6(16.0 g/mol) = 211.62 g/mol

Then convert mols (figured out in step 1) to grams:
(.800mol)(211.6g/ 1 mol) = 169 g --> mols cancel


24. D
Same as above:
M-> molarity which is mol/L so:
1. (0.675mol/L)(1.5L)= 1.0125mol --> liters are canceled

2. find how many grams are in one mol of CH3OH
H: 1.0 g/mol
C: 12.0 g/mol
O: 16.0 g/mol

CH3OH: (12.0 g/mol) + 4(1.0g/mol) + (16.0 g/mol) = 32.0 g/mol

Then convert mols (figured out in step 1) to grams:
(1.0125mol)(32.0g/ 1 mol) = 32.4g --> mols cancel


25. B
Molarity is mol/L so we need to find the number of moles of solute and the number of liters of solution.

1. Find moles:
Li: 6.941g/mol
Cl: 35.45g/mol
O: 16.0 g/mol

LiClO4 : (6.941g/mol)+ (35.45 g/mol) + 4(16.0g/mol) = 106.39g/mol

(17.2g/mol LiClO4)(1mol / 106.39g)= .1617 mol LiClO4

2. Find Liters:
- must convert mL to L

2250mL (1 L / 1000mL) = 2.25L

3. Find molartiy
-find by dividing number of mols (1) by number of liters (2)

(.1617mol / 2.25 L) = .0719M

I hope I helped!!!

Answer 4

i juz can answer 3 qs as i forgot already my basic chem

1.d
23.b
24.d