Can you help me answer these chemisty ?'s?

Question

Is it A B C D or E

These ?'s are not HW, its suppose to help me for the test, the #'s are going to b different but in the same format. so how do u solve them?

1) A solution containing 9.5g of magnesium chloride in water has a volume of 200 ml. the molarity of the magnesium chloride in the solution is

A. 0.0475M

B 0.50M

C 9.5M

D 0.25M

E 1.0M

2) A solution containing 9.5g of MgCI2 in wter has a volume of 200 ml. the molarity of chlorde ions is

A 0.0475M

B 0.50M

C 9.5 M

D 0.25M

E 1.0M

3) Mass % is calculated as the mass of the solute divided by the mass of the solution multiplied by 100

A true

B false

4) If 400 ml of a 0.125M solution of sodium acetate is diluted to exactly 500 ml, the molarity of the resulting sodium would be

A 0.250M

B 0.0500M

C 2.50M

D 0.500M

E 0.100M

50 it would require ____ ml of concentrated (12M) hydrochloric acid to prepare exactly 0.50L of a 0.400 M solution

A 0.0166

B 120.

C100.

D 17

E 12.0

THANK YOU ALL SOOOO MUCH

Answer 1

molarity is moles per liter

so use the info given to figure out how many moles you have in the volume given

1. MgCl2 is 95 g/mol (use a periodic table)

you have 9.5 g, divide by 95 g in a mol, and you get the number of mols you have (.01)

then divide the mols you have by the volume you have (.2 L)

.01/.2 = 0.50 M

Answer 2

1) B

Find the molar mass of MgCl2

(95.211g/mol)

Then (#mols of MgCl2)/0.2L water = 0.50M

2) E

Refer to #1 for amount of MgCl2 (0.50M)

note that for every mol MgCl2 there are 2 mols Cl- ions

Therefore 2*(mols MgCl2) = 1.0M

3) A

Depends on what Mass % it's looking for, I guess.

Wording is confusing and not specific but I don't see why it can't be true.

4) E

0.125M * 400ml/500ml = 0.100M

Because 0.125M*400ml = number of moles of sodium acetate

Then divide it by final volume of solution

5) D

Find the number of moles needed first:

0.50L * 0.400M = 0.20 mol HCl

Now find out what volume of 12M HCl gives you 0.20 mol HCl:

12M * x litres = 0.20 mol

x litres = 0.20/12M = 0.0167 litres

Then convert to mL, which is 0.0167 litres * 1000mL/litre = 17 mL

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There you go,

Goodluck with your test