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

How is percent yield calculated?

1. A(Actual yield ÷ theoretical yield) × 100
2. B(Theoretical yield ÷ actual yield) × 100
3. C(Mass of reactants ÷ mass of products) × 100
4. DActual yield − theoretical yield

What is a single covalent bond?

1. AOne electron transferred from one atom to another
2. BTwo pairs of electrons shared between two atoms
3. CThe attraction between two oppositely charged ions
4. DOne pair of electrons shared between two atoms

DNA belongs to which group of biological molecules?

1. ACarbohydrates
2. BNucleic acids
3. CLipids
4. DProteins

At STP (0 °C and 1 atm), what volume does 1 mole of an ideal gas occupy?

1. A1,0 L
2. B273 L
3. C6,02 L
4. D22,4 L

При постоянной температуре объём газа уменьшили вдвое. Что происходит с его давлением?

1. AОно не меняется
2. BОно уменьшается вдвое
3. CОно удваивается
4. DОно становится в четыре раза меньше

Which coefficients balance __Na + __Cl₂ → __NaCl?

1. A1, 1, 1
2. B2, 1, 2
3. C1, 2, 1
4. D2, 2, 1

Making ammonia (N₂ + 3H₂ ⇌ 2NH₃) is exothermic. A low temperature would give a higher yield, yet factories use a moderately high temperature. Why?

1. AThe catalyst only works when the reaction is endothermic
2. BAt low temperatures the reaction is too slow to be useful
3. CLow temperatures would make the ammonia explode
4. DHigher temperatures shift the equilibrium toward more ammonia

Why does a sodium ion (Na⁺) have almost the same mass as a sodium atom?

1. AThe ion gains a neutron that balances the loss
2. BThe only difference is one electron, which has a tiny mass
3. CThe ion has one fewer proton, which has a tiny mass
4. DIons and atoms always have exactly the same mass