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What is the composition of aqua-regia that corrodes noble metals such as platinum, gold?

Correct Answer: 3 parts of hydrochloric acid and 1 part of nitric acid
The composition of aqua regia is 3 parts of hydrochloric acid and 1 part of nitric acid. It corrodes/dissolves noble metals such as gold, platinum, and palladium.

Given that, 24 carat gold is pure gold, 18 carat gold is 3/4th of pure gold and 20 carat gold is 5/6th of pure gold, the ratio of the pure gold in 18 carat gold to the pure gold in 20 carat gold is -

Directions : In each of the following questions a statement is given, followed by two conclusions. Give answer :

Statements : The Bank of England's move to auction 25 metric tons of gold drew plenty of bidders looking for a bargain, but was criticised by major gold producers worldwide.

Conclusions :
I. The Bank of England should not auction gold which it possesses to keep steady international prices of gold.
II. Bidders should quote higher gold prices to retain present value of gold in the international markets.

Severe corrosion of metals occurred when coupled with platinum is due to the higher current density for hydrogen evolution but not due to the reversible potential of the platinum-platinum ion electrode.

The reversible potential of gold is more positive than platinum in emf series whereas in galvanic series the position of gold is below platinum.

Gold and platinum are mixed in a ratio 8 : 9 to make a ring. Find the ratio of their price in the ring if the price of platinum is 0.7 times the price of gold.

S1: The role of the precious yellow metal is undergoing a dramatic change.
P: In developing countries like India, where gold is used mainly for ornaments, a distinct change in attitude is in the offing.
Q: Slowly, the use of gold in the form of ornaments will be on the decline and even if gold prices shoot up, women folk would not like to sell off their ornaments.
R: The yellow metal will soon be treated as an investment instrument.
S: The maxim, "Larger the gold reserves, richer the country" will not hold good for a long time.
S6: Again, it would not be an economic proposition to buy and sell gold ornaments as an instrument of investment as buying would be costlier and selling will be at a discount.

The Proper sequence should be:

The ratio platinum to silver in a bracelet is 5 : 7. If the price of platinum is 1/10th the price of silver, find the cost of the bracelet if the cost of platinum in the bracelet is 24000 rupees.

In a rare coin collection, all coins are either pure gold or pure silver , and there is initially one gold coin for every three silver coins . With the addition of 10 more gold coins to the collection, the ratio of gold coins to silver coins is 1 to 2. Based on this information , how many total coins are there now in this collection (after the acquisition)?

A certain dentist specializes in implanting gold and silver teeth in his patients mouths .He charges $ 650 for a gold tooth an $ 325. for a silver tooth. If his told fees for implanting gold and silver teeth last week were $ 15, 925 in total and he implanted five more gold teeth that silver teeth, how many teeth in total did he implant over the week?

An alloy of gold and silver weight 50 g. It contains 80% gold. How much gold should be added to the alloy so that percentage of gold is increased to 90 ?