chemis question
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8g of sodium hydroxide were dissolved to form 100cm3 of aqueous solution. what was the concentration in mol/dm3 of this solution (mr of NAOH=40)
1. 0.2mol/dm3
2. 0.5mol/dm3
3. 2.0mol/dm3
4. 5.0mol/dm3
my working - 8/40X(24) i got none of the answers leh
answer is 3 2.0mol/dm3... -
This part of chemistry very maths oneOriginally posted by Fireindahouse:8g of sodium hydroxide were dissolved to form 100cm3 of aqueous solution. what was the concentration in mol/dm3 of this solution (mr of NAOH=40)
1. 0.2mol/dm3
2. 0.5mol/dm3
3. 2.0mol/dm3
4. 5.0mol/dm3
my working - 8/40X(24) i got none of the answers leh
answer is 3 2.0mol/dm3...
1 dm³ = 10 cm * 10 cm * 10 cm = 1000 cm³
So 100 cm³ = 0.1 dm³
Then num of moles = 8/40 = 0.2 mol
Concentration = 0.2 mol / 0.1 dm³ = 2.0 mol / dm³ -
No. of mol of NaOH used = 8/40 = 0.2 mol
100 cm³ = 0.1 dm³
Concentration of solution in mol/dm³ = 0.2/0.1 = 2 mol/dm³
regarding ur working, 8/40X(24)
u can only multiply by 24 dm³ when it is a GAS
the 40 (Mr of NaOH) is NOT the NUMBER OF MOLES, it is the molecular mass of 1 mole of NaOH, therefore even if it is a gas, u are wrong
the 8g is only the amt of NaOH used, not the number of moles of NaOH used, so u need to divide 8g by the Mr of NaOH
hope this helps
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orhh per dm3...
thx -
mol per dm³ (mol divided by the volume ) right. So You divide the No. of mol by the volume ( which is in dm³).Originally posted by Fireindahouse:orhh per dm3...