NY Regents Chemistry Exam June 2019
Part B-1 Questions 31-40
31 The bright-line spectra of four elements, G, J, L, and M, and a mixture of at least two of these elements is given below.
Which elements are present in the mixture?
(1) G and J
(2) G and L
(3) M, J, and G
(4) M, J, and L
Solution: We need to match the white lines in mixture to the line above. We get G and L
Answer: Choice 2
32 Which electron configuration represents an atom of chlorine in an excited state? (1) 2-8-7-2
(2) 2-8-7
(3) 2-8-8
(4) 2-7-8
Solution: In an excited state, one electron jumps from a lower to a higher energy level. Looking at the Periodic Table, the electron configuration for chlorine is 2-8-7 in the ground state. In the excited state, we need to see an electron go to the higher energy such as 2-7-8, an electron went from second to third energy level.
Answer: Choice 4
33 A student measures the mass and volume of a sample of aluminum at room temperature, and calculates the density of Al to be 2.85 grams per cubic centimeter. Based on Table S, what is the percent error for the student’s calculated density of Al?
(1) 2.7%
(2) 5.3% (3) 5.6%
(4) 95%
Solution: In Table S the density of Al is 2.70 g/cm3. % error is (measured -accepted)/accepted *100% according to Table T.
((2.85-2.70)/2.70) *100
Answer: Choice 3
34 Magnesium and calcium have similar chemical properties because their atoms in the ground state have (1) equal numbers of protons and electrons
(2) equal numbers of protons and neutrons
(3) two electrons in the first shell (4) two electrons in the outermost shell
Solution: Elements in the same group has similar chemical properties because they have the same number of valence electrons ( valence electrons are in the outermost shell)
Answer: Choice 4
35 As the elements in Period 2 of the Periodic Table are considered in order from left to right, which property generally decreases?
(1) atomic radius
(2) electronegativity (3) ionization energy
(4) nuclear charge
Solution: Atomic radius decreases from left to right. If not sure, we can look at the elements in period 2 and use Table S to see the trend in atomic radius, electronegativity or ionization energy.
Answer: Choice 1
36 Given the balanced equation for the reaction of butane and oxygen: 2C4H10 + 13O2 → 8CO2 + 10H2O + energy
How many moles of carbon dioxide are produced when 5.0 moles of butane react completely? (1) 5.0 mol
(2) 10. mol
(3) 20. mol
(4) 40. mol
Solution: The coefficients in the equation are 2 for butane and 8 for carbon dioxide. This means for every 2 moles of butane reacted, 8 moles of carbon dioxide will be produced. For 5 moles of butane reacted (5moles of butane*8 mol CO2/ 2 moles butane) moles of CO2 will be produced
Answer: Choice 3
37 What is the percent composition by mass of nitrogen in the compound N2H4 (gram-formula mass = 32 g/mol)? (1) 13%
(2) 44%
(3) 88%
(4) 93%
Solution: The mass of nitrogen on the Periodic Table is 14 g/mol. There are 2 atoms of nitrogen in the formula. We do (2*14g/mol / 32g/mol)*100%
Answer: Choice 3
38 Which ion in the ground state has the same electron configuration as an atom of neon in the ground state?
(1) Ca2+
(2) Cl- (3) Li+
(4) O2-
Solution: Ne has 2-8 electron configuration according to the Periodic Table, or 10 electrons (atomic number is equal to 10. Oxygen has 8 electrons (atomic number is 8) but when it has 2- charge, that means 2 electrons were added, making it 10 electrons total.
Answer: Choice 4
39 The molar masses and boiling points at standard pressure for four compounds are given in the table below.
(2)HCl
(3)HBr
(4)HI
Solution: The higher the boiling point, the stronger the intermolecular forces.
Answer: Choice 1
40 Which particle model diagram represents xenon at STP?
Solution: Xenon is a noble gas and we are looking for a gas particle diagram. Gas particles are far apart from one another, eliminating choice 3 and 4. Furthermore, xenon is not a diatomic gas, eliminating choice 2.
Answer: Choice 1