Exercise

Which of the following reactions represents a double displacement reaction? 

Potassium and calcium are very reactive metals at the top of the series. Because their ions have different charges, ${\mathrm{K}}^{+}$ and ${\mathrm{Ca}}^{2+}$, their compounds behave differently when heated. Their hydroxides are heated. If the compound decomposes, complete the word equation. If it does not decompose, write 'no reaction'.

$\mathrm{potassium} \mathrm{hydroxide} \to$ _____.

$\mathrm{calcium} \mathrm{hydroxide} \to$ _____.

Write the formulae and then balance the following chemical equations.
Ferric chloride+Ammonium hydroxide$\to$Ferric hydroxide+Ammonium chloride

$\mathrm{Acid}+ \mathrm{Metal}\to \mathrm{Salt}+\mathrm{X}$

What is $\mathrm{X}$ in the equation?

Adding which of the following to a colourless solution would give an indication that the solution could possibly be hydrochloric acid?

An acid used by goldsmith for dissolving gold is

Read the following statements:
$\left(\mathrm{P}\right)$ Stainless steel does not rust.
$\left(\mathrm{Q}\right)$ Iron, nickel and chromium form an alloy.
Does statement $\left(\mathrm{Q}\right)$ present a valid explanation for statement $\left(\mathrm{P}\right)$? Justify your answer.

Listed here is the reactivity of certain metals:

From the list above, identify the metal(s) that are likely to be found in a pure state in the Earth's Crust.