Thursday

July 31, 2014

July 31, 2014

Total # Posts: 28

**Math**

A saline solution is 20% salt. How many gallons of water must be added to dilute the mixture to 8 gals of a 15% saline solution? here is my method: using c1V1 = c2V2, (0.2)(V1) = (0.15)(8) V1 = 6 gals So, since 8 gals are required to dilute the saline solution of 15%, 8-6 = 2 ...

**calculus**

Hi sasha, Let me explain the methods step by step : a)3x^2 ln(2x) For this question, product rule must be applied : uv = udv/dx + vdu/dx where u = 3x^2 & v = ln(2x) Differentiate u, du/dx = 6x(I'm sure you know the basic differentiation) Differentiate v ,dv/dx = 2/2x = 1/x...

**Math - Please help**

Hi Christopher, Let me explain the method of solving this problem: Given the area of the ring = 2123 ft^2 The formula for area is pi*r^2, where r is the radius Therefore,we need to find the r based on the area given 2123 ft^2 = pi*r^2 (work this out using calculator) r^2 = (21...

**math**

Hi Teresa, Always remember: ln x = loge(log base e)x log x = log10(log base 10)x Example : ln x = 2 loge x = 2 x = e^2 log x = 5 log10 x =5 x = 10^5 (Hope this two examples have given you a rough understanding) ln(x-4) = -3 ln(x-4) = loge(x-4),right? loge(x-4) = -3 We need to ...

**Separation process**

Oil used to absorb benzene from gas is to be stripped with steam at P = 1atm to recover the benzene.Equlibrium at the operating temperature is approximated using Henry's Law.When the oil contains 10%mol of benzene,the oil's partial pressure is 5.07kPa.The oil is nonvol...

**Chemistry**

Hi Dr.Bob, Which is the correct formula for dinitrobis(ethylenediamine)cobalt(III) nitrate? I'm not sure which is the correct one out of these two: a)[Co(en)2(NO2)2]NO3 or b)[Co(NO2)2(en)2]3(NO3)3 ? At the instance, I've choosen option a). Is my naming correct?

**Chemistry**

When 6200g of ethylene glycol and 16600g terephtalic acid reacted completely to generate poly(ethyleneterephtalate)(PET),how many grams of H20 generated? My working: mol of ethylene glycol = 6200g/(62g/mol) = 100 moles mol terephtalic acid = 16600g/(166g/mol) = 100 moles So,bo...

**Chemistry**

Thank you Dr.Bob & sorry for the inconvenience caused to you

**Chemistry**

Arrange these acids in terms of increasing acidity: CH3COOH, NH3+CH2COOH, CH3CONHCH2COOH Dr.Bob asked me what NH3+CH2COOH is.NH3+CH2COOH is obtained when 1 mol of glycine is added with a very strong acid,which results in both the amino & carboxyl groups to be fully protonated....

**Chemistry**

Ok,that NH3+CH2COOH is obtained when 1 mol of glycine is added with a strong acid,which results in both amino & carboxyl groups to be fully protonated.

**Chemistry**

Dr.Bob, Arrange these acids in terms of increasing acidity: CH3COOH, NH3+CH2COOH, CH3CONHCH2COOH According to my Chem textbook,NH3+CH2COOH has a low pKa value since both the COOH & NH3+ are protonated,so it is most acidic. CH3COOH is a weak acid, but I'm not sure about the...

**Chemistry**

But Dr.Bob,from what I refer,NH3+CH2COOH is the strongest acid since it has both acid and NH3 protonated.Acetic acid is a weak acid,I'm not sure about the CH3CONHCH2COOH. That's what confuses me

**Chemistry**

Arrange these acids in terms of increasing acidity: CH3COOH, NH3+CH2COOH, CH3CONHCH2COOH My answer is CH3COOH,CH3CONHCH2COOH,NH3+CH2COOH . Is this correct Dr.Bob?

**Chemistry**

Disulfide bonds in protein: a) results from an oxidation of thiol b)help to maintain the shape of proteins c)can be broken by reduction d)all of the above I know the option a) is correct,but I'm confused between options b)& c) as the informations on those two r not clear. ...

**Chemistry**

How many stereoisomers are possible for threonine?

**Chemistry**

Ok thank you Dr.Bob

**Chemistry**

How many stereoisomers are there for 1,2-dichlorocyclopentane? The answer options are 1,2,3 & 4. I think it is 4 because there is one cis & one trans isomer,so when using the 2^n formula,the final answer is 2^2 =4.Is my approach correct? Need ur help Dr.Bob.Thanks

**Chemistry**

For a system where: NH2OH + CH3NH3+ --> CH3NH2 + NH3OH+ 95% 95% 5% 5% State of equilibrium in the system is described by the percentages given above.Which of the species above is the strongest acid in the system? My answer is CH3NH3+, is it correct?

**Chemistry**

500.0 mL of 0.220 mol/L HCl(aq) was added to a high quality insulated calorimeter containing 500.0mL of 0.200 mol/L NaOH(aq).Both solutions had a density of 1g/mL & a specific heat of 4.184 J/g.K.The calorimeter had a heat capacity of 850 J/C.Temperature of entire system rose ...

**Chemistry**

Sorry what I meant was dividing the total heat with mole of NaOH ,not mass.

**Chemistry**

Ok,then how do I find the dH of NaOH? Do I need to use the total heat of the system and divide it by the mass of NaOH to get its dH ? I'm still confused Thank you

**Chemistry**

500.0mL of 0.220 mol/L HCl(aq) was added to a high quality insulated calorimeter containing 500.0mL of 0.200mol/L NaOH(aq).Both solutions had a density of 1.000g/mL & a specific heat of 4.184 J/g.K. The calorimeter had a heat capacity of 850.0 J/degree C. The temperature of th...

**Chemistry**

When solving Hess law problems,do we need to use all the equations given to get the Htotal or just choose the relevant equations that are related to the final equation required? Let's say there r 5 equations given,but the relevant equations are 3 only ,so we can neglect th...

**Chemistry**

Given acidity constant,Ka of benzoic acid is 6.28 X 10^-5. pH of 0.15 molar solution of this acid is ? Here is my method: Benzoic acid is a weak acid,hence it dissociates very little. So: C6H5COOH---> C6H5COO- + H+ [H+] and [C6H5COO-] are yet to be calculated,so let them be...

**Chemistry**

So,my second method is correct isn't it? The answer is -78.4kJ?

**Chemistry**

But in the answer options: a) -27.4 kJ b) -72.8 kJ c) -78.4 kJ d) -84.6kJ I attempted this problem in the other way.When using the q =mcdT,I added the mass of both water and sulfuric acid. q = (300g +10.65g)(4.184J/g.K)(6.55C) = 8513.43 J Then, I calculated the mole of sulfuri...

**Chemistry**

But in the answer options: a) -27.4 kJ b) -72.8 kJ c) -78.4 kJ d) -84.6kJ I attempted this problem in the other way.When using the q =mcdT,I added the mass of both water and sulfuric acid. q = (300g +10.65g)(4.184J/g.K)(6.55C) = 8513.43 J Then, I calculated the mole of sulfuri...

**Chemistry**

When pure sulfuric acid is dissolved in water,heat is evolved.To a calorimeter containing 300g of water at 20degree C,10.65g of sulfuric acid also added at the same temperature.The change in temperature,which was monitored by a digital probe with negligible heat capacity cease...

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