Gold has always been a highly prized metal, widely used from the beginning of history as a store of value. It doesn't rust like iron and doesn't become tarnished like silver. It is so chemically inert that it won't react even with the strongest concentrated acids. But it can be dissolved in aqua regia- a fresh-prepared mixture of concentrated {eq}HNO_3 {/eq} and HCl (1:3).

When Germany invaded Denmark in World War II, the Hungarian chemist George de Heresy dissolved the gold Nobel Prizes of Max von Laue and James Franck in aqua ragia to prevent the Nazis from stealing them. He placed the jar with the solution on a shelf in his laboratory, and after the war, precipitated the gold out of the add and returned it to the Royal Swedish Academy of Sciences and the Nobel Foundation who recast the medals and again presented them to Laue and Franck.

The unbalanced equation for the reaction of gold with aqua regia is given below. Add the stoichiometric coefficients to the equation to balance it.

{eq}Au(s)+HNO_3(aq)+HCl(aq) \rightarrow HAuCl_4(aq) + NO_2(g) +H_2O(l) {/eq}

What is the function of HCI?

a. It supplies chloride ions to form a complex ion with the oxidized gold.

b. It acts as an oxidizing agent.

c. It acts as a reducing agent.

Predict the products of the following acid-base reactions, and predict whether the equilibrium lies to the left or to the right of the reaction arrow. part ao2-(aq)+h2o(l)< => express your answer as part of a chemical equation. identify all of the phases in your answer. o2-(aq)+h2o(l) < => oh-(aq)+oh-(aq)part bpredict whether the equilibrium lies to the left or to the right of the equation in previous part. h2o is a stronger acid than oh–, so the equilibrium lies to the right. h2o is a weaker acid than oh–, so the equilibrium lies to the left. h2o is a stronger acid than oh–, so the equilibrium lies to the left. h2o is a weaker acid than oh–, so the equilibrium lies to the right. part cch3cooh(aq)+hs? (aq) < => express your answer as part of a chemical equation. identify all of the phases in your answer. ch3cooh(aq)+hs-(aq) < => h2s(aq)+c2h3o2-(aq)h2s(aq)+c2h3o2-( aq)part dpredict whether the equilibrium lies to the left or to the right of the equation in previous part. ch3cooh is a weaker acid than h2s, so the equilibrium lies to the right. ch3cooh is a weaker acid than h2s, so the equilibrium lies to the left. ch3cooh is a stronger acid than h2s, so the equilibrium lies to the right. ch3cooh is a stronger acid than h2s, so the equilibrium lies to the left. part eno2-(aq)+h2o(l) < => express your answer as part of a chemical equation. identify all of the phases in your answer. no2-(aq)+h2o(l) < => part fpredict whether the equilibrium lies to the left or to the right of the equation in previous part. hno2 is a stronger acid than h2o, so the equilibrium lies to the right. hno2 is a weaker acid than h2o, so the equilibrium lies to the left. hno2 is a stronger acid than h2o, so the equilibrium lies to the left. hno2 is a weaker acid than h2o, so the equilibrium lies to the right.

15. which of the following is not human-caused groundwater pollution? a. water in an aquifer dissolves elements such as arsenic and mercury from surrounding rock. b. water in an aquifer is contaminated by leachate that seeps into the ground from a landfill. c. water in an aquifer becomes polluted with chemicals used in hydraulic fracturing, or fracking. d. water in an aquifer absorbs harmful bacteria from the drainage field of a septic tank.

Why is it possible for different microorganisms to extract energy not only from carbohydrates and other biological molecules but from a large variety of substances?