Chemistry Answers

1.Given below is the dissociation of NH₃ in water having a K_b value of 1.8 × 10^-5. The reaction started with the equilibration of 0.65 M NH₃. A common ion that is 0.25 M NH₄Cl, was added to the initial solution and waited for some time for the reaction to reach equilibrium once again.

NH_3(aq) + H₂O_(l) ↔ NH₄⁺_(aq) + OH^-_(aq)

Determine the pH of the solution given after the addition of the common ion. The K_w of water is 1.0 × 10^-14.

2.What is the pH of a buffer solution that is 0.350 M ethylamine and 0.200 Methylammonium chloride, after the addition of 0.100 M HNO₃? The value of K_b for ethylamine is 4.7 x 10^-4.

identify the given substances if it is polar or non polar , and which type of intermolecular forces they belong

1.H---F

2.

2. Aqueous solutions of silver nitrate and potassium chloride can be mixed to precipitate silver

chloride, Calculate the mass of silver chloride that is formed in the reaction of 9.20 g silver

nitrate with 5.15 g potassium chloride.

Create a Lewis Dot Symbols out of the given elements in each item. Take note of the electron charges of the elements .

1.) B2+

2.) Au+

3.) Ne3-

4.) Cu3-

A solution was made by dissolving 3.75 g of a solute in 108.7 g of acetone . The solution boiled at 56.58° C. The boiling point of pure acetone is 55.95° C, and the Kb =1.71° C/m. What is the molecular weight of the solute?

The molal boiling point constant of water is 0.512ºC/m. If 1 mol cane sugar (342g/mol) is dissolved in 1kg water, the solution will boil at 100.512ºC, assuming standard pressure. By this relationship, half of a mole of sugar (171g) would boil at 100.256 C/m and 2 mol sugar (684g) should boil at 101.024ºC/m. However, these are not necessarily solutions that can be mixed; 684g of sugar is nearly a pound and a half of sugar, which you are supposed to dissolve in a liter of water!

From the given situation above, why is it important to understand the constants relating to water?

The molal freezing point of water is 1.86ºC/m (1.86K/m), which can be expressed as 1.86ºC ● kg H2O/mol solute (1.86K ● kg H2O/mol solute) after some algebraic rearrangement. This means that a solution of 1 mol cane sugar (342g, over 3 4 lb) dissolved in 1kg of water should freeze at -1.86ºC.

Describe the freezing point drop suggests in number 1.

Give two examples of alloys alongwith their compositions and uses.

Calculate the mass (g) of magnesium oxide produced when 500 g of magnesium reacts with oxygen in the air.

2Mg + O2 → 2MgO

Calculate the pH of an acetic acid solution at 3.20 x 10-4 mol/L (% ionization = 1.30%).