General Chemistry Answers

1.    What concentration of NaF do you need to add to a 0.15 M HF solution to get a buffer solution pH of 9.5? The Ka for HF is 7.4x10^-4.

6.4 oz of ZnO is 54% Zn. How many grams of ZnO does it contain?

Considering only ions with charges of +1, +2, -1, and -2, or neutral atoms, give the symbols for 4 species that are isoelectronic with Kr.

Calculate the volume of 0.25 of H2SO4 that will contain a 4.5g of the acid

10cm² of carbon (ii)oxide is sparked with 10cm² of oxygen. if all the volume of gases are measured at STP, calculate the volume of the residual gases after sparking

If 15.65 mL of aq. HCl is required to neutralise 20.00 mL of the sodium carbonate

solution from question 4 above, what is the molarity of the aq. HCl? (Show all steps in

your calculation as set out below.)

(a). Write the reaction equation for the titration.

(b). Calculate the number of moles of Na2CO3 (standard solution) used in the titration.

(c). Using the balanced reaction equation, find the number of moles of HCl that

reacted.

(d). Calculate the molarity of the HCl solution.

Using the localized electron model, decribe the bonding in hydrogen cyanide and phosgene

A sample of ammonium sulphate was heated with 100.0 mL of 0.50mol/L aqueous sodium hydroxide. To ensure that all the ammonium sulphate reacted, an excess of sodium hydroxide was used. Heating was continued until all of the ammonia had been driven off as a gas. The unreacted sodium hydroxide remaining in the solution required 27.3 mL of 0.600mol/L hydrochloric acid for neutralization. Calculate the concentration of the ammonium salt.

Use the localised electron model to describe the bonding in hydrogen cyanide and phosgene (COCl2)

Calculate the ΔH of the following problems:

1) How many joules are required to raise the temperature of 450 mL of water from 30°C to 100°C?

2) The specific heat of copper metal is 0.385 J/g °K. How many kJ of heat are needed to raise the temperature of 1.1 kg block of copper from 27.5°C to 50°C?