Химия для вступительных экзаменов на сестринские программы: лист заданий с ответами

What is the half-life of a radioactive isotope?

1. AHalf the number of protons in the nucleus
2. BThe time taken for the mass of a sample to double in size
3. CThe time taken for half of the radioactive atoms in a sample to decay
4. DHalf the time it takes for all the atoms to decay

What is an unsaturated solution?

1. AA solution that holds the maximum possible solute
2. BA solution that can still dissolve more solute
3. CA solution with undissolved solid at the bottom
4. DA solution with no solute at all

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

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

Which coefficients balance __Na + __Cl₂ → __NaCl?

1. A2, 1, 2
2. B1, 1, 1
3. C1, 2, 1
4. D2, 2, 1

К какому типу относится реакция AgNO₃ + NaCl → AgCl + NaNO₃?

1. AГорение
2. BОбмен
3. CРазложение
4. DЗамещение

A red blood cell is placed in pure water (a hypotonic solution). What happens?

1. AWater leaves the cell, which shrinks and wrinkles
2. BSalt enters the cell, which shrinks
3. CWater enters the cell, which swells and may burst
4. DNothing happens to the cell

Why is gamma radiation used to sterilise sealed medical supplies such as syringes?

1. AIt adds a protective chemical coating to the items
2. BIt passes through the packaging and kills microbes without making the items radioactive
3. CIt is stopped by the packaging, so it only cleans the outside
4. DIt heats the items to very high temperatures, so the microbes are burned away inside the pack

В воздушном шаре 2,0 л газа при 300 K. При постоянном давлении его нагревают до 450 K. Каков новый объём?

1. A3,0 л
2. B1,3 л
3. C4,5 л
4. D2,0 л