Užduočių lapas tema Chemija slaugos stojamiesiems egzaminams su atsakymais

Which is a sign that a chemical reaction may have taken place?

1. ASugar dissolves completely when stirred into water
2. BA block of wax melts when it is heated
3. CWater freezes into ice when put in a freezer
4. DA gas is produced when two liquids are mixed

What does the law of conservation of mass state?

1. AMass is neither created nor destroyed in a chemical reaction
2. BThe mass of products is always greater than the mass of reactants
3. CGases have no mass
4. DMass is lost as heat in every reaction

What is a precipitate?

1. AA substance that speeds up a reaction
2. BA liquid that forms when a solid melts
3. CA gas that bubbles out when two solutions are mixed
4. DAn insoluble solid that forms when two solutions react

For the gas reaction N₂ + 3H₂ ⇌ 2NH₃, what is the effect of increasing the pressure?

1. AThe equilibrium shifts to the left, toward N₂ and H₂
2. BThere is no effect on the equilibrium
3. CThe equilibrium shifts to the right, toward NH₃
4. DThe NH₃ breaks down completely

Kuris pokytis padarytų, kad kreidos gabalėlis greičiau reaguotų su rūgštimi?

1. AKreidos susmulkinimas į miltelius
2. BVieno didelio kreidos gabalo naudojimas
3. CRūgšties atšaldymas šaldytuve
4. DRūgšties praskiedimas daugiau vandens

What is the name of the molecular compound CO?

1. ACarbon oxide
2. BCarbon monoxide
3. CCarbon dioxide
4. DMonocarbon oxide

Burning a match is strongly exothermic, so why does it not catch fire until it is struck?

1. AStriking makes the reaction endothermic
2. BStriking pushes extra oxygen into the chemicals of the match head
3. CStriking supplies the activation energy to start the reaction
4. DThe match must first absorb all its energy from the air

A mixture contains sand, salt and water. Which sequence separates all three?

1. ADistil first to remove the sand, then filter out the salt
2. BFilter to remove the sand, then distil the filtrate to collect water and leave salt
3. CEvaporate all the water first, then filter the salt away from the dry sand
4. DUse a magnet to remove the salt, then filter the sand