Chemistry, Third edition

REVISION QUESTIONS 99

6.4.Write chemical andionic equations for the reaction of:

(i) magnesium carbonate with dilute sulfuric acid

(ii)ammonium sulfate and hot sodium hydroxide

(iii)sodium sulfide and dilute nitric acid

(iv)sodium sulfite (a preservative) and vinegar.

6.5.(i) Much more CO 2 (g) is produced annually than

SO 2 (g), yet SO 2 (g) causes greater damage to limestone

buildings than CO 2. Why?

(ii)The reaction of calcium hydroxide solution (limewater)

with carbon dioxide is the basis of the limewater testfor CO 2.

During the reaction, a white precipitate is produced. Name

the precipitate and write an ionic equation for the reaction.

6.6.An insoluble blue solid, containing an anion J and a

cation K, fizzed violently with dilute sulfuric acid, producing a

clear blue solution B. The gas produced had no smell and

solution B gave a blue precipitate with sodium hydroxide

solution. Identify J and K. Explain your reasoning.

6.7.A solution of a simple salt GH contains a cation G and an

anion H. GH gave a red-brown precipitate when mixed with

sodium hydroxide solution. GH gave a brown ring with con-

centrated H 2 SO 4 and FeSO 4. Identify the cation and anion pre-

sent.

6.8.A simple salt ST (containing an anion S and a cation T)

is insoluble in water. ST produced hydrogen sulfide when

warmed with hydrochloric acid. The resulting solution was

divided into two. One half gave a white precipitate with

sodium sulfate solution. The other half produced a white

precipitate with sodium hydroxide solution which was soluble

in excess NaOH. Identify S and T. Explain your reasoning and

include ionic equations for any reactions that occur.

6.9.The detrimental effect of acid rain upon fish is partly due

to the release of toxic aluminium ions (Al^3 (aq)) under acidic

conditions. Explain this by writing ionic equations which

show what happens to Al^3 (aq) ions in (i)an alkaline

environment,(ii)in a previously alkaline environment which

has been overwhelmed with acid rain.

Extension material to support this unit is available on our website.

DID YOU KNOW?

The ‘liquid gold’ that the Nazis missed

The Danish laboratory of the famous physicist Niels Bohr was a

safe haven for Jewish scientists during the early part of the Sec-

ond World War. Bohr had donated his own Nobel Prize (200 g of

23 carat gold) to charity, but two other Nobel prize winners left

their inscribed medals with him in 1940, just before Denmark

was invaded by Germany.

Fearful that the medals would be discovered by the invading

Nazis, one of Bohr’s colleagues came up with the idea of dis-

solving the medals in acid and storing the gold solution (‘liquid

gold’) on the laboratory shelf with other chemicals. Despite a

thorough search in Bohr’s laboratory, the gold survived unde-

tected and new medals were cast after the war.

Gold is resistant to most acids but a fuming mixture of concentrated hydrochIoric and nitric acids,

known as Aqua Regia(meaning ‘Royal Water’) does dissolve gold and this was the acid used in Bohr’s

laboratory.