January 2003 Regents #21-30

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Questions 1-10 Questions 11-20 Questions 21-30 Questions 31-40 Questions 41-50


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Answer Explanations
21 When a mixture of water, sand, and salt is filtered, what passes through
the filter paper?

(1) water, only
(2) water and sand, only
(3) water and salt, only
(4) water, sand, and salt

3 the salt will dissolve in the water and pass through the filter paper
22 A hydrate is a compound that includes water molecules within its
crystal structure. During an experiment to determine the percent by
mass of water in a hydrated crystal, a student found the mass of the
hydrated crystal to be 4.10 grams. After heating to constant mass, the
mass was 3.70 grams. What is the percent by mass of water in this crystal?

(1) 90.%      (3) 9.8%
(2) 11%       (4) 0.40%

3 mass water= 4.10-3.70=0.40g


23 Which of these 1 M solutions will have the highest pH?

(1) NaOH        (3) HCl
(2) CH3OH      (4) NaCl

1 high pH is a base 

NaOH (OH-) is a base

24 Which physical property makes it possible to separate the components
of crude oil by means of distillation?

(1) melting point      (3) solubility
(2) conductivity        (4) boiling point

4 distillation use boiling point differences 
25 In saturated hydrocarbons, carbon atoms are bonded to each other by

(1) single covalent bonds, only
(2) double covalent bonds, only
(3) alternating single and double covalent bonds
(4) alternating double and triple covalent bonds

1 saturated hydrocarbons-all single bonds-alkanes
26 Which formula correctly represents the product of an addition reaction
between ethene and chlorine?

(1) CH2 Cl2       (3) C2 H4 Cl2
(2) CH3 Cl        (4) C2 H3 Cl

3 C2H4 + Cl2 -->C2 H4 Cl2
27 When a neutral atom undergoes oxidation, the atomís oxidation state

(1) decreases as it gains electrons
(2) decreases as it loses electrons
(3) increases as it gains electrons
(4) increases as it loses electrons

4 ox # increase-loses electrons
2 2H+ --> H2o
1 2 reactants and the isotopic notations
4 acid base salt --> aqueous


Questions 1-10 Questions 11-20 Questions 21-30 Questions 31-40 Questions 41-50

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