For many years the recovery of gold—that is, the separation of gold from other materials—involved the use of potassium cyanide:     Au + KCN + O2 + H2O à  KAu(CN)2 +  KOH     (a) Balance the above chemical equation. (b) What is the minimum amount of potassium cyanide in grams needed to extract 29.0 g (about an ounce) of gold?

How many moles of nitrogen gas would be produced if 3.23 moles of copper(II) oxide were reacted with excess ammonia in the following chemical reaction? 2 NH,(g) + 3 CuO (s) → 3 Cu(s) + N,(g) + 3 H,O(g)

If the furnace initially contained 22.122.1 kg of solid calcium oxide and 10.110.1 kg P4O10(l)P4O10(l), how many kilograms of calcium phosphate were produced during the purification of the iron?

Balance the following equations: (a) SO2 + O2 ------>SO3 (b) Li2O(s) + H2O(l) ------> LiOH(aq) (c) Na + H2O ------> NaOH + H2

Which of the following reactions does the chemical equation below best represent? 3 Cu(CI), (aq) + 2 Al (s) → 3 Cu (s) + 2 AICI, (aq) formation of copper(ll) oxide upon heating a solution containing copper(Il) hydroxide O reaction of copper (II) oxide with hydrochloric acid O reaction of copper(l) nitrate with sodium hydroxide O reaction of copper(ll) chloride with elemental aluminum

Home-Grown Example: Calculation of Mass-Related Concentrations (a) A solution is made by dissolving 1.675 mg of sucrose (C₁2H22011) in 0.01091 g of water. What is the mass percentage of each component of the solution? (b) A 1762-kg sample of groundwater was found to contain 2.443 µg of Fe²+. What is the concentration of Fe²+ in parts per billion?

When 25 g of lead (II) nitrate, Pb(NO3)2, is mixed with 15 g of sodium iodide in water, a reaction occurs and this produces sodium nitrate and solid lead (II) iodide. (a) Write a balanced equation for the reaction. (b) Calculate the theoretical amount of lead (II) iodide produced.

A 235.2-g sample of ground water is analyzed for calcium. The Ca2+ in the sample is first precipitated and filtered-off as NH4CaPO4·7H2O. This precipitate is dried and heated, releasing water and ammonia to yield anhydrous calcium pyrophosphate (Ca2P2O7). The mass of Ca2P2O7 obtained is 0.0234 g.Give the calcium content of the ground water in parts per million (to three significant figures).

Balance the following chemical equations (include the states of matter): The reaction between elemental phosphorus P4(s) and O2(g) to make P4O10(s):

Does the mass of the dried product(s) agree with the table included and the chemical equation: CaCO3(aq) + 2CH3COOH(aq) --> Can(CH3COO)2(aq) + CO2(g) + H2O(l)? if not, how can you account for the mass loss or excess mass? (Hint: No calculations needed)