General Chemistry Answers

Calculate the mass percent of carbon, nitrogen and oxygen in acetamide, C2H5NO

A sample of 89.1 g of tetraphosphorous decoxide (P4⁢O10) reacts with 49.0 g of water to produce phosphoric acid (H3⁢PO4) according to the following balanced equation.

P4O10+6H2O⟶4H3PO4

Determine the limiting reactant for the reaction.

Calculate the mass of H3⁢PO4 produced in the reaction.

Calculate the percent yield of H3⁢PO4 is isolated after carrying out the reaction.

A 5.00 L of a gas is collected at 100. K and then allowed to expand to 20.0 L. What must the new temperature be in order to maintain the same pressure (as required by Charles' Law)?

An aqueous potassium iodate stock solution is made by dissolving 6.33 mol KIO in sufficient water for the final volume of the solution to be 4.80 L.

Calculate the molarity of the stock KIO3 solution.

A 10.0 mL aliquot is removed from the described stock solution and diluted to a total volume of 100.0 mL. Calculate the molarity of the dilute solution.

A chemist places 0.550 g KCl in a flask and adds water until the total volume is 0.900 L. Calculate the molarity of the solution.

What is the concentration in millimolar (mM)?

. 2.83 g of a sample of haematite iron ore [iron (III) oxide, Fe₂O₃] were dissolved in concentrated hydrochloric acid and the solution diluted to 250 cm³. 25.0 cm³ of this solution was reduced with tin(II) chloride (which is oxidised to Sn⁴⁺ in the process) to form a solution of iron(II) ions. This solution of iron(II) ions required 26.4 cm³ of a 0.0200 mol/dm³ potassium dichromate(VI) solution for complete oxidation back to iron(III) ions.

(a) given the half–cell reactions 

(i) Sn⁴⁺_(aq) + 2e^– ==> Sn²⁺_(aq)

and (ii) Cr₂O₇^2–_(aq) + 14H⁺_(aq) + 6e^– ==> 2Cr³⁺_(aq) + 7H₂O_(l)

deduce the fully balanced redox equations for the reactions

(i) the reduction of iron(III) ions by tin(II) ions

(ii) the oxidation of iron(II) ions by the dichromate(VI) ion

(b) Calculate the percentage of iron(III) oxide in the ore. 

8. Use the half-reaction method to balance the following equation and then identify the oxidizing and reducing agents:

Fe(OH)2 (s) + Pb(OH)3 -(aq) → Fe(OH)3 (s) + Pb(s) [basic]

In the course of doing valuable biomedical research one day, let's say you make a salt solution by adding 1 mol of NaCl to 90 g of water. 

What is the percent by mass (i.e. mass %) of the solution? 

What is the molality of a solution composed of 40.0 g sodium nitrate (NaNO3) and 500.0 g of water? 

Borax, continued:

An aqueous solution of Borax (Na2B4O7) is sometimes used to fireproof wood. 

How many moles of Na2B4O7 are in 600.0 ml of a 1.57 M Na2B4O7 solution?