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### Determining mass for solutions

Posted: **Sat Nov 06, 2021 11:24 am**

by **IneedhelpwithChem**

Hi everyone. I have an assignment which requires me to solve this.

"Determine the mass of KClO_{3} required to make a 0.5M solution. Atomic masses: K = 39, Cl =35.5, O = 16"

Can someone please tell me what steps I need to go through to get the answer, what do I need to find? I know how to calculate molar mass and such, i'm just not sure of the steps I need to take to get the answer for the question.

Thanks in advance.

### Re: Determining mass for solutions

Posted: **Sat Nov 06, 2021 11:49 am**

by **ChenBeier**

0,5 M means 0,5 mol/l

Calculate molar Mass, this the weight for 1 mol. Calculate then for 0,5 mol. This mass put in a measured flask and fill up to 1l with water

### Re: Determining mass for solutions

Posted: **Sat Nov 06, 2021 11:54 am**

by **IneedhelpwithChem**

Molar mass of KCLO_{3} is 39 + 35.5 + 16(x3) = 125.5

= 125.5g/ 1 mole

this is what I have so far, what next?

### Re: Determining mass for solutions

Posted: **Sat Nov 06, 2021 12:06 pm**

by **ChenBeier**

No

The molar mass is not correct its 122,5 g/mol, but can you read above.

There is it written how to go further.

### Re: Determining mass for solutions

Posted: **Sat Nov 06, 2021 12:12 pm**

by **IneedhelpwithChem**

yes, so I have to divide the moral mass in half to get the answer for .5 mol? and then add water?? I don't understand completely

### Re: Determining mass for solutions

Posted: **Sat Nov 06, 2021 12:18 pm**

by **ChenBeier**

Yes it is the half of this amount. This has to be dissolved in water to get 1 l.

### Re: Determining mass for solutions

Posted: **Sat Nov 06, 2021 12:22 pm**

by **IneedhelpwithChem**

wow........guess I overcomplicated it, thank you so much

### Re: Determining mass for solutions

Posted: **Sat Nov 06, 2021 12:29 pm**

by **IneedhelpwithChem**

Molar mass of KCLO_{3} is 39 + 35.5 + 16(x3) = 122.5

= 122.5g per 1 mole solution

Molar mass of KCLO_{3} for 0.5M solution = 122.5g divided by 2

= 61.25g per .5 mole solution

### Re: Determining mass for solutions

Posted: **Sat Nov 06, 2021 12:34 pm**

by **ChenBeier**

IneedhelpwithChem wrote: ↑Sat Nov 06, 2021 12:29 pm
Molar mass of KCLO

_{3} is 39 + 35.5 + 16(x3) = 122.5

= 122.5g per 1 mole solution

Molar mass of KCLO

_{3} for 0.5M solution = 122.5g divided by 2

= 61.25g per .5 mole solution

The Molar mass is 122,5 g/mol. The mass of 0,5 mol is 61,25 g.

After dissolving it in water up to 1 l!!!! it is 0,5 mol/l