This is a timed quiz. You will be given 60 seconds per question. Are you ready?
Answer: 3.5 grams The half-life of a substance is the amount of time required for that substance to decay to half of its original mass. In the context of this question, 6 hours represents two half-lives. Therefore, the substance will decay to one-fourth of its original mass, or 3.5 grams.
The passing sight distance for a section of 60 mph 2-lane rural highway with a 1,740-ft vertical sag curve where a bridge passes over at 16.8 ft is 2,273 ft. Solution: Use sag vertical curve length at undercrossing equation (US Customary units) S = sigh distance = L/2 + [400(C-5.75)]/A Where: L = vertical sag length = 1740 ft C = bridge height = 16.8 ft A = % difference in grades = 3.15 And 5.75 = 0.5(object height + eye height) S = 1740/2 + [400(16.8-5.75)]/3.15 = 2,273 ft
The statement, “Sizing is based on the measured flow conditions” is not correct when considering the surface overflow rates of primary settling tanks. Typically, the primary settling tanks are sized based on the surface area calculations performed using 1) design average flow conditions and 2) design peak hourly flow conditions. The larger surface area of the two is used to size the primary setting tank. Specific design requirements for primary settling tanks are set by state regulating agencies.
All of the listed issues are potential safety and/or operational issues associated with a bridge spanning a recently repaved roadway that now a vertical clearance of 4-inches less than posted. Drivers of large vehicles depend on the posted clearance values to avoid collisions with the bridge structure. Collisions with overhead structures often lead to multiple crashes due to limitations on stopping site distances, design speeds, and traffic conditions. Traffic delays may result from overhead structure collisions, multiple vehicle crashes and repairs to the damaged structure.
Answer: Supersaturated When a saturated solution is heated so more solute can be dissolved, the solution is described as supersaturated. Supersaturated solutions are typically unstable, and the solute can crash out of solution if a seed crystal is provided.
Answer: CH3COOH A weak acid is an acid that does not dissociate completely in solution. HCL, HBr, HClO4, and H2SO4 are strong acids. CH3COOH is the weak acid.
Answer: 7 Begin this problem by considering the oxidation state of oxygen. As in most oxides, oxygen has an oxidation state of -2. Multiply this value by four to account for all of the oxygens, giving a total oxidation value of -8. Potassium has an oxidation state of +1, bringing the total oxidation value to -7. In order to maintain electrical neutrality, chlorine must have an oxidation state of +7.
Answer: .40 The mole fraction for a compound indicates (moles of given compund) / (total moles of system). In this question, there are two moles of NaOH and five total moles in the system. Thus, the mole fraction is expressed as 2/5, or .40.
Answer: C2H6 Saturated straight-chain hydrocarbons contain only single bonds. As long as the saturated hydrocarbon does not contain a ring, it will obey the formula CnH2n+2. Thus, the saturated straight-chain hydrocarbon is C2H6.
Answer: Malleability Malleability refers to a metal’s ability to be hammered into sheets.
AASHTO assumes that the height of a driver’s eye and the height of an object above pavement are 42 inches and 24 inches (respectively) when developing recommendations for minimum stopping sight distances. AASHTO’s recommended distances are a conservative estimate of how long it will take a driver to perceive a situation exists that will require them to stop, apply the brakes, and come to a complete stop. The stopping site distance is an important safety consideration to assure that drivers have a continuous length of visible roadway.
Answer: C2H4 Hydrocarbons with the formula CnH2n contain double bonds. The only compound with this formula, C2H4, must contain a double bond.
Answer: Na2O Metallic oxides consist of an oxygen atom bound to a metal. The only metal present in this question is sodium, so Na2O must be a metallic oxide.
The proper sequence of steps to construct a dewater wellpoint system are as follows: 1. Jet wellpoints into the ground 2. Fill annular void with filter media 3. Connect wellpoints to header pipe with riser 4. Connect header pipe to suction pumps A wellpoint system used to dewater a construction excavation consists of a series of small-diameter wells that are closely spaced and installed at shallow depths. The wells are connected to a piping system that is attached to a vacuum pump and surrounds the excavation.
Answer: 4 grams The half-life of a substance is the amount of time required for the substance to decay to half of its original mass. In the context of the question, 19.5 hours represents three half-lives. Therefore, the substance will be reduced to (1/2)3 or 1/8 its original mass. 1/8 x 32 gives the correct answer of 4 grams.
A split-spoon is not a hammer used for conducting SPTs. A split spoon is a sampling tube, approximately 20 - 36-inches long, that is placed inside a drill rod to collect soil samples. Automatic, donut, and safety hammers are used to drive the drill rods into the soil.
AASHTO’s recommended stopping sight distances are based on the operation of a passenger car. In general, large trucks require a longer stopping distance than a passenger car. However, since drivers in large trucks sit higher up than a driver in a car, they are able to see substantially further down a roadway. AASHTO does not provide recommendations for bicycle or railroad car SSDs.
When drinking treating water, the presence of a poor taste or unpleasant odor, or the awareness of an ambient water temperature may indicate that there is a water quality problem within a finished water storage facility. Stale water within a storage facility promotes the growth of microorganisms that cause poor tastes or unpleasant odors and is often a result of water stored too long. Stagnant water will approach ambient temperatures, and may be a result of short-circuiting or accumulated sediment that impedes mixing within a storage unit.
The total volume of the grit chamber is 2,079 ft3 when required to handle an average flow of 3 million gallons per day (mgd), with a peak flow ratio of 2.5 and a detention time of 3 minutes. Solution: volume of grit chamber = peak flow x detention time Where peak flow = average flow x peak flow ratio = 3 mgd x 2.5 = 7.5 mgd Given 1 mgd = 1.54 ft3/sec Where detention time = 3 min x 60 sec/min = 180 sec Volume = 7.5 mgd x 1.54 ft3/sec x 180 sec = 2,079 ft3
Cathodic protection is used to control corrosion. Corrosion is an electrochemical process in which an electrical current flows through a metallic substance, causing a chemical reaction that results in pitting and, ultimately, complete deterioration. Cathodic protection systems use the electrical properties of metallic substances to protect against the corrosion of metallic piping and structures by forcing an electrical interaction. There are two main types of cathodic protection systems: - Galvanic - uses a sacrificial anode, placed adjacent to the structure to be protected, that corrodes instead of the structure - Impressed current - a current is applied to a structure from an adjacent anode
