Nizomiy nomidagi tdpu tabiiy fanlar fakulteti

Moddaning molyar massasi son jihatdan uning massasining atom birligining ifodalangan qiymatiga teng va M harfi bilan ifodalanadi. Mol esa modda miqdorini ifodalashning asosiy usuli bo ‘lib, bu 0.012 kg (12kg) uglerodda echta uglerod atomi bo ‘lsa, tarkibidagi shuncha zarracha bo ‘lgan moddaning miqdorlaridir.
V=m/M bundan M=m/V m=M
4. Mol.Molyar massa, Modda miqdoriga doir masalalar yechish
1-masala.Quyidagi moddaning nisbiy molekulyar massasini hisoblang: Ca(OH)₂, Na₂SO₄, Ba(NO₃)₂, H₃PO₄.
Yechish: Moddaning nisbiy molekulyar massasini hisoblang.
Mr (NA₂SO₄)=2Ar(Na)+Ar(S)+4Ar(O)=2x23+2x16+2x1=40+32+22+74m. a. b.
Mr (Na₂SO₄)=2Ar(NA)+Ar(S)+4Ar(O)+2x23+32+4x16=32+64=142 m.a.b.
Mr(Ba(NO₃)₂)=Ar(Ba)+2Ar(N)+6Ar(O)=137+2x14+6x16=137+28+96=261.m.a.b.
Mr(H₃PO₄)=3Ar(H)+Ar(P)+4Ar(O)=3x1+31+4x16=31+64=98
2-masala.49 g sulfat kislota necha molni tashkil qilishini hisoblang.
Yechish. 1-usul. Moddaning nisbiy molekulyar massasini hisoblaymiz:
Mr(H₂SO₄)=2Ar(H)+Ar(S)+4AR(O)=2x1+32+4x16=32+64=98.m.a.b.
V=m/M
Tenglamadan foydalaniib 49 g sulfat kislota necha molni tashkil qilishini hisoblaymiz:
V=m/M=49/98=0.5 mol.
2-usul. Masalani proporsiya usulida ham yechish mumkin.
Dastlab sulfat kislotaning nisbi molekulyar massasini hisoblaymiz:
Mr(H₂SO₄)=2Ar(H)+Ar(S)+4Ar(O)=2x1+32+4x16=2+32+64=98m.a.b.
98g H₂SO₄---------1 mol
49 gH₂SO₄---------x mol x mol=49 g 1 mol/98=0.5 mol.
3-masala.Gramm-mol massasi 80 g bo‘lgan CuO ning 0.3 mol miqdorida qancha gramm bo‘ladi?
Dastlab sulfat kislotaning nisbiy molekulyar massasini hisoblaymiz:
Mr(CuO)=Ar(Cu)+Ar(O)=64+16=80 m.a.b. yoki gramm/mol.