What is the typical carat value of gold used in jewelry?

$2Na_{(s)} + 2H_2O_{(l)} \longrightarrow ?$

$(a)$ Why does calcium start floating when added to water?
$(b)$ Most metals do not release hydrogen gas when reacting with nitric acid. Why?
$(c)$ Write the chemical equation for the reaction of iron with steam. Name the compound of iron obtained.

Define alloys. List the properties of alloys that make them useful over pure metals. Explain this fact with suitable examples.

$(a)$ What type of ores are calcined? Illustrate by giving a suitable example.
$(b)$ In what form is the calcined ore obtained,and how can it be reduced? Give chemical equations of the reduction process involved for the example provided by you.
$(c)$ Name two metals used as reducing agents by displacing metals of lower reactivity from their compounds.

Name a non-metal which is lustrous and a metal which is non-lustrous.