Junior Science Olympiad Atoms and Molecules — practice questions
22 free MCQs with worked solutions. Tap any question for the answer + explanation, or practice them all in the app.
Practice Junior Science Olympiad Atoms and Molecules in the app →A sealed flask is weighed before and after a reaction inside it. The total mass:Water from a river, a well and a tap all give hydrogen and oxygen in the mass ratio:Decomposing 9 g of water always gives 1 g of hydrogen and how much oxygen?Nitrogen and hydrogen in ammonia are always present in a mass ratio of:The law of definite proportions was first stated by the chemist:The atomic theory explaining both laws of chemical combination was given by:According to Dalton, the tiny particles that take part in chemical reactions are:Dalton's postulate that atoms cannot be created or destroyed explains the law of:Dalton held that atoms of one element are identical in mass and in their:Dalton said atoms combine to make compounds in ratios that are:Later work showed Dalton was wrong about one point, because atoms are made of:Since 1961 the standard reference chosen for measuring atomic masses has been:One atomic mass unit is defined as a mass equal to what share of a carbon 12 atom?The combining capacity of an element, which tells how its atoms link up, is its:A group of atoms carrying a charge, such as sulphate, is called a:Adding up the atomic masses of every atom in a molecule gives its:Hydrogen has atomic mass 1 u and oxygen 16 u. The molecular mass of water is:Using H as 1, N as 14 and O as 16, the molecular mass of nitric acid works out to:For sodium chloride, whose particles are ions, chemists calculate the:With Na as 23 and Cl as 35.5, the formula unit mass of common salt is:The SI unit used for the amount of a substance is the:One mole of any substance contains how many particles, to four figures?