timtamboy63 Posted November 20, 2011 Report Share Posted November 20, 2011 Yeah, Drake is right.A salt formed by a weak base + strong acid = acidic (low pH)A salt formed by a weak base + weak acid = close to neutral (pH = ~7)A salt formed by a strong base + weak acid = basic (high pH) 1 Reply Link to post Share on other sites More sharing options...
robawalsh Posted November 23, 2011 Report Share Posted November 23, 2011 A 1 molar solution is a solution in which 1 mole of a compound is dissolved in a total volume of 1 litre.The molecular weight of ethanol (C2H5OH) is 46, so one gram molecular weight (= 1 mole) is 46g. If you dissolve 46g of ethanol into a volume of 1 litre, you have made a 1M ethanol solution.Hence, dividing the volume by 20 to get 50cm3 would mean that we need 46g/20=2.3g of ethanol to make a 1M solution in a volume of 50cm3. So, place a beaker on the scales and set the scales to zero, then pour pure ethanol in until you have exactly 2.3g. Then top the beaker up with pure water until you have 50cm3. You should now have 50cm3 of 1 mol/cm3 of ethanol.Is this correct? Reply Link to post Share on other sites More sharing options...
ILM Posted November 23, 2011 Report Share Posted November 23, 2011 Yes you are right:you know that:c= n/v if you need concentration to be 1 M and the volue that you have is 0.05 then you need 0.05 molif 1 mol= 46 g then n.M=m = 0.05(1/20)*46 = 2.3 2 Reply Link to post Share on other sites More sharing options...
Marta Wasiolka Posted November 26, 2011 Report Share Posted November 26, 2011 I need to determine the concentration of an unkown acidic solution using NAOH solution of known concentration ( 0.1000 +- 0.0004). It is titration experiment. I used phenolophtalein. I obtained exactly 10.0mL of acidic solution and pour it into 0.5L, filled it in using destillated water. To beaker I put twenty ml of solution prepared one step earlier. titre are ten.eight. ten.seven .. ten.eight. mean titre is ten.seventy six. how should i calculate the concentration? sory that the titrations are by words not by numbers but something is wrong with my computer Reply Link to post Share on other sites More sharing options...
kiwi.at.heart Posted November 26, 2011 Report Share Posted November 26, 2011 I need to determine the concentration of an unkown acidic solution using NAOH solution of known concentration ( 0.1000 +- 0.0004). It is titration experiment. I used phenolophtalein. I obtained exactly 10.0mL of acidic solution and pour it into 0.5L, filled it in using destillated water. To beaker I put twenty ml of solution prepared one step earlier. titre are ten.eight. ten.seven .. ten.eight. mean titre is ten.seventy six. how should i calculate the concentration? sory that the titrations are by words not by numbers but something is wrong with my computerFirst you work out how many moles of NaOH you used which is n = concentration of NaOH x mean volume of titreOnce you have the moles of NaOH you will know how many moles of acid was in your sampleThen its just Concentration of acid = moles/ volume of acid (0.01) 1 Reply Link to post Share on other sites More sharing options...
Emmi Posted December 2, 2011 Report Share Posted December 2, 2011 I have an energetics question on lattice enthalpies: Which one of the following compounds would be expected to have the highest lattice enthalpy? A. Na2O B. MgO C. CaO D. KCl Any explanation would be great, as my teacher didn't really cover lattice enthalpy well. Reply Link to post Share on other sites More sharing options...
Drake Glau Posted December 6, 2011 Report Share Posted December 6, 2011 I have an energetics question on lattice enthalpies: Which one of the following compounds would be expected to have the highest lattice enthalpy? A. Na2O B. MgO C. CaO D. KCl Any explanation would be great, as my teacher didn't really cover lattice enthalpy well. The one with the highest electronegativity difference. Lattice enthalpy is basically the amount of energy you need to put the atoms together. Or in other words, the enthalpy of formation for ionic compounds since they make lattices. 1 Reply Link to post Share on other sites More sharing options...
dessskris Posted December 6, 2011 Report Share Posted December 6, 2011 what are the factors affecting potential difference in voltaic cells, anyone? Reply Link to post Share on other sites More sharing options...
nametaken Posted December 6, 2011 Report Share Posted December 6, 2011 I've done this IA. You could potentially (joke lol) look at varying concentrations of electrolytes, mass of electrodes, surface area of electrodes (you could change the surface area and avoid also changing the mass by simply folding the strip of metal used as an electrode), length of salt bridge..... 1 Reply Link to post Share on other sites More sharing options...
Guest Animistic Anaemia Posted December 6, 2011 Report Share Posted December 6, 2011 I've done this IA by varying the compound on the salt bridge and it actually worked as there were different voltages for each salt used Reply Link to post Share on other sites More sharing options...
dessskris Posted December 7, 2011 Report Share Posted December 7, 2011 I've done this IA. You could potentially (joke lol) look at varying concentrations of electrolytes, mass of electrodes, surface area of electrodes (you could change the surface area and avoid also changing the mass by simply folding the strip of metal used as an electrode), length of salt bridge..... I know you have, and when I saw the questions given by my teacher I was like :evilsmirk: thank you so much, I'll think about it! I've done this IA by varying the compound on the salt bridge and it actually worked as there were different voltages for each salt used my teacher suggested me to do this as well when I consulted with her. thanks. Reply Link to post Share on other sites More sharing options...
Hinuku Posted December 17, 2011 Report Share Posted December 17, 2011 Hi, I have a problem with nucleophilic substitution, namely SN1 reactions. What I read is that the alkyl groups surrounding the carbon bonded to the halogen have a positive inductive effect meaning that they push electrons away from them, making the carbon slightly negative and themselves slightly positive. So now I'm wondering why is the carbon in carbocations positive? I'm not really sure - is it that the whole carbocation is positive? (not just the carbon) or maybe that the halogen is so electronegative that it attracts the excess of electrons of the central carbon and then attracts even more making it positive... I really can't understand this... I would be very thankful for any help Reply Link to post Share on other sites More sharing options...
Drake Glau Posted December 18, 2011 Report Share Posted December 18, 2011 If I remember right the C gives electrons to the halogen which is what causes the halogen to go away. Even if the alkyl groups are pushing e- to the carbon (is this from further organic option? O.o) the carbon would be pushing them to the halogen resulting on the slightly positive transition state. Your electronegativity idea also makes since and probably does play a factor in the process also. 1 Reply Link to post Share on other sites More sharing options...
msb143 Posted January 1, 2012 Report Share Posted January 1, 2012 Does anyone have any practice Chemistry questions i could have? Reply Link to post Share on other sites More sharing options...
Emmi Posted January 1, 2012 Report Share Posted January 1, 2012 Does anyone have any practice Chemistry questions i could have? Some textbooks will have sample problems at the end of the book or at the end of each chapter you can practice with. I know that the Pearson Baccalaureate book does (it's what I use). If yours has sample problems or you can get your hands on a study guide or something that would be good. Plus you could always ask your teacher for past exams or questions, I'm sure he/she will have some. Or you could try using to search for past chemistry exams, which will have actual past Paper 1, Paper 2, and Paper 3 questions on them. Reply Link to post Share on other sites More sharing options...
Vexation Posted January 23, 2012 Report Share Posted January 23, 2012 Hello! I need help with the "Solutions" unit in Chemistry 20 (11th grade)I am very confused about all the different units and formulas needed to solve this problem and I would be very thankful if you could walk me through this question explaining everything in as much detail as possible:The concentration of fluoride ions, F-, in municipal drinking water should not exceed 1.5 ppm. What is the maximum mass of fluoride ions that can be dissolved in 500mL of water, while not exceeding this limit? Reply Link to post Share on other sites More sharing options...
ILM Posted January 23, 2012 Report Share Posted January 23, 2012 I know the following that 1 ppm= 1mg/l, so you are talking about 1.5 mg of F-/ l of water. Since you are talking about 0.5 l then your talking about 0.75 mg of F- . This all depends on the fact that 1ppm=1 mg/l if not then it is only a conversion factor. 1 Reply Link to post Share on other sites More sharing options...
Reader Digest Posted February 8, 2012 Report Share Posted February 8, 2012 Hello, I'm a little bit confuse with my latest topic which is Macromolecules."Glycerol can react with three molecules of stearic acid, to form a triglyceride. Deduce the number of carbon atoms in one molecule of this triglyceride."Any help would be much appreciated! Reply Link to post Share on other sites More sharing options...
Hinuku Posted February 10, 2012 Report Share Posted February 10, 2012 Hi, I am wondering why maximum values are sometimes put in ranges. I'm talking about a value of a trace metal for which a tolerable limit was set but it is given as a range (1 - 5 not just 5). I just can't figure out what this may mean. Thank You Reply Link to post Share on other sites More sharing options...
Drake Glau Posted February 10, 2012 Report Share Posted February 10, 2012 Hello, I'm a little bit confuse with my latest topic which is Macromolecules."Glycerol can react with three molecules of stearic acid, to form a triglyceride. Deduce the number of carbon atoms in one molecule of this triglyceride."Any help would be much appreciated!Count the number of carbons in glycerol and 3 stearic acids. Add them all together and you're done. When the 3 stearic acids react with the glycerol it is only the H and OH that react so there is no loss in carbons whch is why you can just count up all the carbons and be done. 1 Reply Link to post Share on other sites More sharing options...
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