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

According to the Arrhenius definition, what does a base produce in water?

1. AHydrogen ions (H⁺)
2. BHydroxide ions (OH⁻)
3. CChloride ions (Cl⁻)
4. DCarbonate ions (CO₃²⁻)

An instant cold pack feels cold when the substance inside dissolves. How is this dissolving process classified?

1. AExothermic
2. BA neutralisation reaction
3. CEndothermic
4. DA combustion reaction

What is a cation?

1. AA neutral atom
2. BA molecule with no charge
3. CA positively charged ion
4. DA negatively charged ion

Which type of bond holds the two atoms together in a nitrogen molecule, N₂?

1. AA double covalent bond
2. BA triple covalent bond
3. CAn ionic bond
4. DA single covalent bond

Why must temperatures be in kelvin in gas law calculations?

1. ACelsius can only be used for liquids
2. BKelvin values are always below 100
3. CGas volume and pressure are proportional to the absolute temperature
4. DThe kelvin scale has smaller degrees, which gives more precise answers

Какова плотность тела массой 50 г и объёмом 20 см³?

1. A1000 г/см³
2. B0,4 г/см³
3. C70 г/см³
4. D2,5 г/см³

Why are the radioactive tracers used for medical imaging usually chosen to have short half-lives?

1. AThey stay active for many years, so a single dose can be used for every future scan
2. BThey emit only alpha particles, which are harmless inside the body
3. CShort half-life isotopes are not radioactive
4. DThey give a strong signal for imaging but leave the body's tissues exposed only briefly

Marble chips react with hydrochloric acid, giving off CO₂. The gas is produced quickly at first, then more and more slowly. Why does the rate fall?

1. AThe products act as a catalyst that slows the reaction down
2. BThe activation energy steadily increases as the reaction goes on
3. CThe acid concentration falls as it is used up, so collisions become less frequent
4. DThe CO₂ produced turns back into acid