Chemistry Answers

A water sample is not alkaline to phenolphthalein however 25ml of the sample on titration required 4.5ml , 0.02N HCL for methyl orange end point. Determine the types and amount of alkalinity present in the sample? (Find P&M, amount of alkalinity)

The N in a 0.4984-g sample of organic material is converted to NH₄HSO₄ by digestion with concentrated H₂SO₄. If the NH₄⁺ ions are precipitated as (NH₄)₂PtCl₆ and the precipitate is ignited to Pt, what is the percentage of N in the sample if the Pt weighs 0.1876 g?

Calculate the pH of a solution which contains 2.0 x 10-3 M sodium acetate and 3.3 x 10-2 M acetic acid in a liter solution. The pKa is 4.74.

What is the ratio of the salt & acid concentration if the solution has a pH of 4.5 & pKa of 4.76?

Calculate the pH of a solution which contains 3.7 x10−2 mole of HAc & 4.8 x 10−2 mole of Na Ac in a liter of solution containing pka 9.26.

A buffer is prepared using 0.28 M HNO2 and 0.23 M NO2 − . The pKa for HNO2 is 3.34. What is the pH of

this buffer after the addition of 0.05 M HCl?

) Calculate the entropy change at a constant pressure of 1 atm when one mole of liquid 

NH3 at -40 is transformed to the gaseous state at 200 using the following data: ℃ ℃

Cp for NH3 (l) = 17.9 Cal K-1 mol-1 ; Cp for NH3(g) = (8.04 + 7.0 x 10-4 T + 5.1 x 10-6

T 2

 )Cal K-1 mol-1 ; Boiling Point of NH3 (g) = 239.7 K; ΔvapH239.7 = 5560 Cal mol-1

) In the solid state at 0 K, nitric oxide is capable of existing in two orientations such as 

NONO and NOON, which have equal probabilities. Calculate the molar entropy of 

NO at 0 K?

How would you test for the presence of the following ions in aqueous solution of an unknown salt? kindly provide name of the test and a balanced chemical equation...Ag^2+

The freezing point of benzene is 5.5oC. What is the freezing point of a solution of 5.00 g of naphthalene (C10H8) in 444 g of benzene (Kf of benzene = 4.90oC/m)