Name: Niña Leizyl B. Mendez Year & Section: BSEE 4 – H Subject: Engineering Science and Applied Sciences Date: September 17, 2023 CHEMISTRY 10.) Find the mass of an oxygen gas, π2 molecule. A.53.1π₯10−24 π B. 50.4π₯10−30 π C. 45.2π₯10−22 π D. 48.4π₯10−27 π Solution: πππ π ππ ππππππ’ππ = πππ π ππ π2 = πππππ πππ π π΄π£ππππππ ′ π ππ’ππππ 2 × 16 π/πππ 6.022 × 1023 πππ −1 πππ π ππ π2 = 50.4 × 10−30 π 20.) A compound used to whiten teeth has the empirical formula HO. The molecular mass of this compound is 34 amu. What is the molecular formula? A. π»2 π3 B. π»3 π3 C. π»2 π2 D. π»3 π2 Solution: π = πππ’ πππ πππππ πππ π ππ π»π = 1 πππ’ + 16 πππ’ πππππ πππ π ππ π»π = 17 πππ’ Divide the molecular mass of the compound by the molar mass of the empirical formula. 34 πππ’ =2 17 πππ’ Multiply the subscripts of the empirical formula by the whole number. ππππ’ππ = πππππ ππ π πππ’π‘π πππππππ‘π¦ ππππ’ππ = 0.5 πππ 2 πππ/πΏ ππππ’ππ = 0.25 πΏππ‘πππ = 250ππΏ 29.)Calculate the mass of water required to prepare a 4m aqueous solution of ππ»3 using 25 g of ππ»3 . A. 0.329kg B. 0.347 kg C. 0.368 kg D. 0.356 kg Solution: Calculate the moles of NH3 present in 25 g of NH3. πππ π ππ ππ»3 πππππ ππ ππ»3 = πππππ πππ π ππ ππ»3 25 π πππππ ππ ππ»3 = π π (14 ) + 3 (1 ) πππ πππ πππππ ππ ππ»3 = 1.47 πππ Calculate the volume of a 4M NH3 solution required to dissolve 25 g of NH3. ππππ’ππ = πππππ ππ π πππ’π‘π πππππππ‘π¦ ππππ’ππ = 1.47 πππ = 0.368 πΏ 4πππ/πΏ Calculate the mass of water required to prepare the required volume of NH3 solution. π»π × 2 = π»2 π2 Densiy of water = 1.00 g/mL = 1 kg/L 23.) What is the volume of 2M solution that contains 0.5 mol of solute? A. 400 mL B. 250mL C.200mL D.500mL Solution: 2π = 2 πππππ = 2πππ/πππ‘ππ πππ π ππ π€ππ‘ππ = ππππ’ππ × π€ππ‘ππ ππππ ππ‘π¦ πππ π ππ π€ππ‘ππ = 0.368 πΏ × 1.00 πππ π ππ π€ππ‘ππ = 0.368 ππ π ππΏ 60.) What is the substance that changes color at a certain pH range? A. Litmus paper B. Balancer C. Indicator D. Lichen Indicators are substances whose solutions change color due to changes in pH. These are called acid-base indicators. They are usually weak acids or bases, but their conjugate base or acid forms have different colors due to differences in their absorption spectra. https://chem.libretexts.org/Bookshelves/Physical_and_Theor etical_Chemistry_Textbook_Maps/Supplemental_Modules_(P hysical_and_Theoretical_Chemistry)/Acids_and_Bases/Acid/I ndicators 71.) Which noble gas has the smallest atomic number? A. Argon B. Neon C. Krypton D. Helium Looking at the periodic table of elements, Helium has the smallest atomic number which is 2, while neon, argon and krypton have 10, 18, and 36, respectively. 89.) When a solid has crystalline structure, the atoms arranged in repeating structures called ? A. Lattice B. Crystal C. Unit cell D. Domain The regular repeating pattern that the atoms arrange in is called the crystalline lattice. https://www.ndeed.org/Physics/Materials/Structure/solidstate.xhtml 118.)When the solution contains less solute particles than the maximum amount the solvent can dissolve at the temperature, the solution is? A. unsaturated B. supersaturated C. saturated D. undersaturated A saturated solution is a solution that contains the maximum amount of solute that can be dissolved under the condition at which the solution exists. https://byjus.com/chemistry/saturated-solution/ 147.) What alkali metal is usually used for x-ray apparatus because of its ability to allow x-rays to pass through with minimum absorption? A. Magnesium B. Beryllium C. Radium D. Barium Because of its low density and low atomic mass, beryllium has very low absorption of X-rays. As a result, it allows X-rays to pass through while also having enough strength to maintain the vacuum (i.e., free space) required for the X-ray tube to operate. https://chemistrytalk.org/beryllium-element/ 176.) Compounds of carbon in hydrogen containing only carbon-carbon single bonds. A. Alkynes B. Alkenes C. Alkanes D. Alkali Hydrocarbons with only carbon-to-carbon single bonds (C–C) and existing as a continuous chain of carbon atoms also bonded to hydrogen atoms are called alkanes https://guides.hostos.cuny.edu/che120#:~:text=Hydrocarbons %20with%20only%20carbon%2Dto,alkanes%20(or%20saturat ed%20hydrocarbons). 205.) When copper turns green, It is an example of its? A. chemical property B. mechanical property C. physical property D. electrical property It is possible to argue that the change in color of copper when it turns green is a physical property. After all, we are observing a change in the appearance of the substance without changing its chemical composition. However, the change in color is actually caused by a chemical reaction between the copper and the oxygen and other substances in the air. Therefore, it is more commonly considered to be a chemical property. https://www.expii.com/t/physical-vs-chemical-changedefinition-examples-11032 234.) The particles of sugar dispersed in water are so small that a clear homogeneous mixture. What is this homogeneous mixture called? A. Colloid B. Suspension C. Compound D. Solution Sugar and water form a solution when mixed. The sugar becomes evenly distributed throughout the solution, so that one portion is not sweeter than another. https://www.edu.xunta.gal/ftpserver/portal/S_EUROPEAS/FQ /3rdESO_archivos/Mixtures_Solutions.htm#:~:text=Solutions %20are%20common%20types%20of,is%20not%20sweeter%2 0than%20another. 263.) When John Newlands made a list of the elements in the 1860’s he ? A. noticed the list seemed far longer than he remembered B. wrapped the list around his favorite mineral sample C. saw that the elements lined up and repeated in groups of eight D. saw similarities between elements and called it the Newlands rule John Alexander Reina Newlands in 1863–64 noted that every eighth element showed similar physical and chemical properties, when the elements are placed in the increasing order of their atomic masses. This was called the Newlands law of octaves. The law states that when elements are placed in the increasing order of atomic masses, the properties of the eighth elements are repeated. https://www.simply.science/images/content/chemistry/struct ure_of_matter/dev_of_periodic_table/conceptmap/Newland s_Law.html#:~:text=Newlands%20Law%20of%20Octaves&tex t=John%20Newlands%20In%201863%2C%20John,its%20physi cal%20and%20chemical%20properties. 292.) Most cosmetics and ointments and creams used in medicines are A. emulsions B. foams C. gels D. sols Emulsions are frequently used in pharmaceuticals, personal hygiene products, and cosmetics. These are usually oil and water emulsions, albeit dispersed. https://www.ncbi.nlm.nih.gov/books/NBK559084/
