Chemistry: Matter and Energy
Which may be heterogeneous? (1) a substance (2) an element (3) a compound (4) a mixture
Answer: (4) a mixture Explanation: A heterogeneous mixture is a mixture with a non-uniform composition. The composition varies from one region to another with at least two phases that remain separate from each other, with clearly identifiable properties. If you examine a sample of a heterogeneous mixture, you can see the separate components.
Which element has the greatest density at STP? (1) calcium (2) carbon (3) chlorine (4) copper
Answer: Explanation: Degree of consistency measured by the quantity of mass per unit volume.
After 418 Joules of heat energy were added to 10 g of water, the final temperature of the water was 40*C. The initial temperature was: (1) 10*C (2) 30*C (3) 40*C (4) 100*C
Answer: Explanation: Specific heat is the amount of heat required to raise one gram of any substance one degree Celsius or Kelvin. The formula for specific heat is the amount of heat absorbed or released = mass x specific heat x change in temperature. specific heat temperature calorie.
Which temperature is equal to 20 K? (1) -253*C (2) -293*C (3) 253*C (4) 293*C
Answer: (1) -253*C Explanation: K= 273 + C
Which is the equivalent of 750. Joules? (1) 0.750 kJ (2) 7.50 kJ (3) 75.0 kJ (4) 750. kJ
Answer: (1) 0.750 kJ Explanation: The kilojoule is an SI (International System of Units) derived unit of energy that is equal to 1000 joules. The joule is defined as the amount of energy transferred to an object when a one-newton force acts on an object in the direction movement through a distance of one meter.
At STP, which list of elements contains a solid, a liquid, and a gas? (1) Hf, Hg, He (2) Cr, Cl2, C (3) Ba, Br2,B (4) Se, Sn, Sr
Answer: (1) Hf, Hg, He Explanation: Solid is the state in which matter maintains a fixed volume and shape; liquid is the state in which matter adapts to the shape of its container but varies only slightly in volume; and gas is the state in which matter expands to occupy the volume and shape of its container.
Which statement describes a chemical property of hydrogen gas? (1) Hydrogen gas burns in air. (2) Hydrogen gas is colorless. (3) Hydrogen gas has a density of 0.000 09 g/cm3 at STP. (4) Hydrogen gas has a boiling point of 20. K at standard pressure.
Answer: (1) Hydrogen gas burns in air. Explanation: At standard temperature and pressure, hydrogen is a nontoxic, nonmetallic, odorless, tasteless, colorless, and highly combustible diatomic gas with the molecular formula H2. Hydrogen is also prevalent on Earth in the form of chemical compounds such as hydrocarbons and water.
Matter that is composed of two or more different elements chemically combined in a fixed proportion is classified as: (1) a compound (2) an isotope (3) a mixture (4) a solution
Answer: (1) a compound Explanation: A compound is a substance composed of two or more different elements that are chemically combined in a fixed proportion. A chemical compound can be broken down by chemical change.
The temperature at which a substance in the liquid state freezes is the same as the temperature at which it: (1) melts (2) sublimes (3) boils (4) condenses
Answer: (1) melts Explanation: Freezing and melting. Freezing is the change that occurs when a liquid changes into a solid as the temperature decreases. Melting is the opposite change, from a solid to a liquid as the temperature increases. These are both examples of changes in the states of matter of substances.
The average kinetic energy of molecules in two gas samples can best be compared by measure: (1) temperatures (2) volumes (3) pressures (4) densities
Answer: (1) temperatures Explanation: Temperature is a measure of the average kinetic energy of all the molecules in a gas. As the temperature and, therefore, kinetic energy, of a gas changes, the RMS speed of the gas molecules also changes. The RMS speed of the molecules is the square root of the average of each individual velocity squared.
The temperature of a sample of water increases from 30* C to 40* C as 418 Joules of heat are added. What is the mass of the sample of water? (1) 1 g (2) 10 g (3) 100 g (4) 1000 g
Answer: (2) 10 g Explanation: Specific heat capacity is the amount of heat energy required to raise the temperature of a substance per unit of mass. The specific heat capacity of a material is a physical property. It is also an example of an extensive property since its value is proportional to the size of the system being examined. mass = energy (J) divided by (specific heat capacity x temperature change). The specific heat of water is 1 calorie/gram °C = 4.186 joule/gram °C which is higher than any other common substance. As a result, water plays a very important role in temperature regulation. The specific heat per gram for water is much higher than that for a metal, as described in the water-metal example.
The difference between the boiling point and the freezing point of pure water at standard pressure is: (1) 32 K (2) 100 K (3) 273 K (4) 373 K
Answer: (2) 100 K Explanation: Boiling point elevation is the raising of a solvent's boiling point due to the addition of a solute. Similarly, freezing point depression is the lowering of a solvent's freezing point due to the addition of a solute. In fact, as the boiling point of a solvent increases, its freezing point decreases.
If 418 Joules are added to 20. g of water at 20. *C, what will be the final temperature of the water? (1) 25*C (2) 30*C (3) 40*C (4) 50*C
Answer: (2) 30*C Explanation: Specific heat is the amount of heat required to raise one gram of any substance one degree Celsius or Kelvin. The formula for specific heat is the amount of heat absorbed or released = mass x specific heat x change in temperature. specific heat temperature calorie.
Which is the most common property of all liquids? (1) definite shape (2) definite volume (3) high compressibility (4) high chemical energy
Answer: (2) definite volume Explanation: Liquids have fixed volume but no fixed shape.They have fixed volume but they do not have fixed or definite shape. If you take 100 ml of water, pour water in a cup, it will take the shape of the cup. Now pour the liquid from cup to a bottle, the liquid has changed its shape and now it has taken the shape of bottle.
A dilute, aqueous potassium nitrate solution is best classified as a: (1) homogeneous compound (2) homogeneous mixture (3) heterogeneous compound (4) heterogeneous mixture
Answer: (2) homogeneous mixture Explanation: A homogeneous mixture is simply any mixture that is uniform in composition throughout. As long as each substance is mixed in enough to be indistinguishable from the others, it is a homogeneous mixture.
At which Celsius temperature does lead change from a solid to a liquid? (1) 874°C (2) 601°C (3) 328°C (4) 0°C
Answer: (3) 328°C Explanation: The melting point (liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at a standard pressure such as 1 atmosphere or 100 kPa.
Which statement describes a chemical property of the element magnesium? (1) Magnesium is malleable. (2) Magnesium conducts electricity. (3) Magnesium reacts with an acid. (4) Magnesium has a high boiling point.
Answer: (3) Magnesium reacts with an acid. Explanation: The surface of magnesium metal is covered with a thin layer of oxide that helps protect the metal from attack by air. Once ignited, magnesium metal burns in air with a characteristic blinding bright white flame to give a mixture of white magnesium oxide, MgO, and magnesium nitride, Mg3N2.
Bronze contains 90 to 95 percent copper and 5 to 10 percent tin. Because these percentages can vary, bronze is classified as: (1) a compound (2) an element (3) a mixture (4) a substance
Answer: (3) a mixture Explanation: A mixture is a substance made by combining two or more different materials in such a way that no chemical reaction occurs. A mixture can usually be separated back into its original components. Some examples of mixtures are a tossed salad, salt water and a mixed bag of M&M's candy.
A sample composed only of atoms having the same atomic number is classified as: (1) a compound (2) a solution (3) an element (4) an isomer
Answer: (3) an element Explanation: An element is a substance whose atoms all have the same number of protons: another way of saying this is that all of a particular element's atoms have the same atomic number. Elements are chemically the simplest substances and hence cannot be broken down using chemical reactions.
At room temperature, a mixture of sand and water can be separated by: (1) ionization (2) combustion (3) filtration (4) sublimation
Answer: (3) filtration Explanation: Filtration is the process of separating suspended solid matter from a liquid, by causing the latter to pass through the pores of some substance, called a filter. The liquid which has passed through the filter is called the filtrate.
Which is a chemical property of water? (1) it freezes (2) it decomposes (3) it evaporates (4) it boils
Answer: (3) it evaporates Explanation: The chemical formula of a molecule of water is H2O: two atoms hydrogen (H2) linked to one atom oxygen (O). The atom electrons (particles with a negative charge) establish links between themselves. Oxygen is more able to keep them close to it than hydrogen. The water molecule results to be charged negatively near the atom of oxygen and positively near the atom of hydrogen. Since opposites attract, the water molecules tend to join together like magnets.
Which element is a solid at STP and a good conductor of electricity? (1) iodine (2) mercury (3) nickel (4) sulfur
Answer: (3) nickel Explanation: Any of the set of metallic elements occupying a central block in the periodic table. Chemically they show variable valence and a strong tendency to form coordination compounds, and many of their compounds are colored.
Which Kelvin temperatures represent the normal freezing and boiling point of water? (1) 0 K and 273 K (2) 0 K and 100 K (3) 100 K and 273 K (4) 273 K and 373 K
Answer: (4) 273 K and 373 K Explanation: The normal freezing point of water is 0 degree Celsius and the normal boiling point of water is 100 degree Celsius. To convert these temperatures to Kelvin, you will add 273 to them. Thus, the freezing point of water at Kelvin temperature is 273K and the boiling point of water in Kelvin is 373 K.
Which is a mixture? (1) CCl4 (l) (2) CaCl2 (s) (3) HCl (g) (4) NaCl (aq)
Answer: (4) NaCl (aq) Explanation: An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending to the relevant chemical formula.
A 10.0-gram sample of which element has the smallest volume at STP? (1) aluminum (2) magnesium (3) titanium (4) zinc
Answer: (4) zinc Explanation: Since all of these elements are under the same conditions, volume only varies based on the number of atoms present. You can find the number of atoms in a given sample by dividing the weight of the sample by the molar mass. Aluminum has a molar mass of 26.9 so 10/26.9 = .371 moles go on to get Ti= 10 / 47.88 =.209 moles Mg = 10.0 / 24.3 = 0.412 moles Zn = 10 / 65.37 = .153 moles Since there are less moles of Zn, it has the smaller volume at STP than the other elements.
