FREE GACE Chemistry Test Questions and Answers
At 25 °C and 101 kPa of pressure, 1,000 mol of He gas is inflated into a weather balloon. What is the weather balloon's volume?
Explanation:
In order to solve for V, the ideal gas rule PV = nRT is rearranged, yielding V = nRT/P. The Celsius temperature must be converted to Kelvin by adding 273 to 25°C to achieve 298 K, where R is the gas constant, 0.08206 L atm/mol K. It is necessary to convert the pressure to atmospheres, where 101 kPa is equivalent to 1 atm (0.9967 atm). V = 1,000 mol x (0.08206 L atm/mol K) (298 K) / 1 atm, where V = 24, 453 L, is the result of plugging the numbers into the equation. The conversion of a liter to a cubic decimeter (dmx3) yields V = 24.5m3.
Holding a liquid at its freezing point and allowing it to slowly harden. Which of the following descriptions of this incident is accurate?
Explaination:
Since freezing is an exothermic process, heat must be released. Throughout the process, the material's temperature at the freezing point is unaffected.
At 110 °C and 1 atm of pressure, a cylinder contains 1 mole of argon and 1 mole of water. The cylinder's temperature drops to -5°C. Which of the following statements regarding the cylinder's contents is truest?
Explanation:
As the temperature drops to -5°C, the water vapor condenses to a liquid, and then to a solid. The vapor pressure of a solid is much less than that of the corresponding gas. The argon is still a gas at -5°C, so almost all the pressure in the cylinder is due to argon.
Which of the following claims regarding liquids' and gases' physical characteristics is accurate? I. Both gases and liquids can be compressed. II. Gases do not flow, but liquids do. III. Gases are incompressible and liquids flow. IV. Gases can be compressed and liquids flow. V. Liquids are incompressible and gases flow.
Explanation:
Liquids and gases both flow since they are fluids, but only gases can be compressed. A gas can be compressed into a smaller volume because the molecules that make up the gas are very far apart from one another.
A mole of an ideal gas is heated to 25 °C and compressed to 10 L. What is the gas's pressure?
Explanation:
Using the appropriate units to plug the data into the ideal gas law yields the right result in atmospheres, which in this case is 2.4 atm. P - nRT/V is the formula. P is therefore determined to be 1 mol (0.08206 L atm/mol K)/298 K / 10 L. When L is used as the volume unit, the R value, which gives the pressure in atm, is 0.08206 L atm / mol K.
4 moles of oxygen, 3 moles of nitrogen, and 7 moles of neon are present in a 10 L cylinder. The cylinder's temperature is raised from 20°C to 40°C. Calculate the percentage of the total neon partial pressure in the cylinder.
Explanation:
The partial pressure of neon will always be 50% of the total pressure, regardless of the temperature, because there are 7 moles of neon out of a total of 14 moles of gas in the cylinder.
Cooling occurs to a gas with constant volume. Which gas-related claim must be accurate?
Explanation:
The relationship between the kinetic energy of gas molecules and temperature is direct. The molecular mobility increases as the temperature drops. Not all temperature drops result in a gas condensing into a liquid. Since no material was added or removed, and the volume stayed unchanged, neither the mass nor the density were affected.
Which substance has the greatest chance of being a solid at STP?
Explanation:
According to IUPAC, Na (sodium) is a solid at standard conditions of 0°C (273.15 K) and 100 kPa (0.987 atm). The possibility of a material being a solid increases with the strength of the intermolecular forces. Noble gases Kr and Xe have very little intermolecular attraction. NH3 possesses some hydrogen bonds, but at STP, it is still a gas. Since metallic bonding holds sodium's atoms together, it is an alkali metal and a solid at STP.
What link between two different materials can be best determined using Graham's law?
Explanation:
By comparing the masses of two distinct gases, one can use Graham's law of diffusion to determine the relative diffusion rate between them.
Which of the following assertions best sums up the periodic table of elements' electronegativity trend?
Explanation:
Near the upper right of the periodic chart are the atoms that are the most electronegative. In contrast to Cesium, which is near the bottom left of the table, fluorine has a high electronegativity.
It is heated from 50° C to 80 ° C. Which of the following assertions regarding the solubility of solids and gases in the liquid is generally accurate?
Explanation:
The solubility of the solid increases as the temperature of the liquid increases, while the solubility of the gas decreases as temperature increases.
Which is the proper sequence for increasing the attraction forces between molecules?
Explanation:
London dispersion forces are the weakest intermolecular forces. These interactions happen in all molecules because of an unequal distribution of electrons around the nucleus, which results in a momentary dipole. Dipole-dipole interactions are interactions between two polar molecules. The negative section of a different molecule is pulled to the original molecule's more positive area. To generate hydrogen bonds, a more potent form of dipole-dipole interaction, a hydrogen atom from one molecule interacts with a nitrogen, oxygen, or fluorine atom from another. Hydrogen bonds can only be created by molecules containing HF, HO, or HN bonds. Ionic bonding is the most potent intermolecular force. In ionic molecules, a positive ion is pulled to a negative ion. The ions in NaCl are entirely charged and firmly linked to one another in an organized crystalline network.
At STP, two moles of hydrogen and one mole of oxygen gas are mixed together in a closed container. Which of the ensuing assertions is accurate?
Explanation:
The partial pressure of hydrogen will be higher since there are twice as many oxygen molecules present. Despite the fact that there are more moles of hydrogen present, the mass of hydrogen will not be greater than the mass of oxygen since oxygen has a higher molecular weight. The volume of each gas will be the same. In the container, hydrogen and oxygen gas can live without mixing to form water. No evidence of a chemical reaction has been provided.
Each flask containing the three liquids X, Y, and Z is suspended in a water bath that is 75°C. Each liquid's boiling point is as follows: Z, 360 K X, 273 K Y, 340 K Which of the three liquids will reach boiling point at a temperature of 75 °C?
Explanation:
Add 273 to convert from degrees Celsius to Kelvin; 75°C equals 348 K. X and Y will both boil in the water bath because they both have lower boiling temperatures. Never will Z get hot enough to boil.
Which of the following actions might raise a solution's freezing point? I. Divide the mixture between two different containers. II. To boil off some of the solvent, heat the solution. III. Start a reaction that will result in some of the solute precipitating.
Explanation:
The amount of solute in a solution has an adverse relationship with its freezing point. The qualities of the solution won't change if it is divided. Heating effectively raises the concentration and lowers the freezing point by evaporating some of the solvent. The concentration will be lower and the freezing point will rise if some of the solute precipitates out.
400 mL of solution are created once 100 g of H3PO4 are dissolved in water. What is the solution's normality?
Explanation:
Instead of the solute concentration, normality refers to the concentration of acid equivalents (H+ ions). The MW of 100 g of phosphoric acid is 98 g/mol. As a result, there are 1.02 moles of phosphoric acid in solution at 100g/98g/mol. The solution has a total volume of 0.4 L, making its molarity 1.02 mol/0.4 L = 2.55 M. For every mole of phosphoric acid, there are three acid equivalents, hence the normalcy is 3 X 2.55 = 7.65 N.