Question 1200803
.
Find the mole fraction of this given problem: a.An NH3
solution made up of 30.0 g of NH3 in 70.0 g of water.
The density of the solution is 0.982 g/mL.
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<pre>
    DEFINITION

        Mole fraction X is the ratio of moles of one substance in a mixture 
        to the total number of moles of all substances. 

    https://www.google.com/search?q=mole+fraction&rlz=1C1CHBF_enUS910US910&oq=mole+fraction&aqs=chrome..69i57j0i131i433i512l2j0i512l7.2120j0j15&sourceid=chrome&ie=UTF-8

    
NH3 Molecular Weight  17.031

Number of moles in 30 g:   {{{30/17.031}}} = 1.76149.


H2O Molecular Weight  18.01528

Number of moles in 70 g:   {{{70/18.01528}}} = 3.88559.


The mole fraction (the answer to the problem's question) is  {{{1.76149/(1.76149+3.88559)}}} = 0.31193 (rounded).
</pre>

Solved, answered and explained.


The post-solution note:  the given density of the solution 0.982 g/mL is EXCESSIVE, NON-NECESSARY and IRRELEVANT.