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Caffeine is a stimulant found in coffee.

caffeine

Which formula represents caffeine?

A

$\mathrm{C}_{7} \mathrm{H}_{10} \mathrm{~N}_{4} \mathrm{O}_{2}$

B

$\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{~N}_{3} \mathrm{O}_{2}$

C

$\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{~N}_{4} \mathrm{O}_{2}$

D

$\mathrm{C}_{8} \mathrm{H}_{11} \mathrm{~N}_{4} \mathrm{O}_{2}$

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The relative atomic mass, $A_{\mathrm{r}}$ , of an element is determined by comparing the mass of one atom of the element with the mass of one atom of element Q.

What is Q ?

A

carbon

B

chlorine

C

hydrogen

D

oxygen

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Caffeine is a stimulant found in coffee.

Figure for Question 3 — CAIE IGCSE Chemistry

caffeine

Which formula represents caffeine?

A

$\mathrm{C}_{7} \mathrm{H}_{10} \mathrm{~N}_{4} \mathrm{O}_{2}$

B

$\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{~N}_{3} \mathrm{O}_{2}$

C

$\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{~N}_{4} \mathrm{O}_{2}$

D

$\mathrm{C}_{8} \mathrm{H}_{11} \mathrm{~N}_{4} \mathrm{O}_{2}$

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A compound of element X has the formula $\mathrm{X}_{2} \mathrm{O}$ and a relative formula mass of 144 . What is element X ?

A

copper, Cu

B

gadolinium, Gd

C

sulfur, S

D

tellurium, Te

CAIE IGCSE Chemistry 3 Stoichiometry Topic Practice

Question 1

Question 2

Question 3

Question 4