12) A sample of sandy water from the seashore is best classified asa A) compound

Question

12) A sample of sandy water from the seashore is best classified asa A) compound B) element C) heterogeneous mixture D) (n) 13) The concentration of which component of the atmosphere has increased dramatically since 1900? A) argon B) carbon dioxide C) nitrogenD) oxygen 14) Elements in the same column on the Periodic Table: A) react similarly C) have the same number of electrons B) have the same weight D) have the same number of neutrons 15) What is the chemical symbol for calcium? 16) When the equation below is balanced, the coefficient of Oz is: A) 2 GGD) Ca CeHe +O2-CO2+ H2O B) 6. C) 8. D) 12 17) In the stratosphere, oxygen (Oa) is converted to ozone (O) by high energy ultraviolet light thus: 02 03 When the equation is balanced using whole number coefficients, the coefficient of oxygen is: A) 1 B) 2 C) 3. D) 4. 18) The label which indicates that a substance is dissolved in water solution is A) (aq) B) (g) D) (w) 19) In the reaction CHs + 202-> CO2+ 2 H20 how many moles of oxygen are required to bum 64.0 g of CH4? A) 2.0 B) 4.0 C) 8.0 D) 128. 20) The major component of dry air is A) argon. B) oxygen. C) nitrogen. D) carbon dioxide. 21) A solution that is 1% by mass contains A) 1 g of solute in 1 kg of solution. B) 10 g of solute in 1000 g of solution. C) 1 mole of solute in 1 L of solution. D) 1 mL of solute in 100 mL of solution. 22) Which of these is a chemical change? A) an acid and a base neutralizing each other. B) gasoline evaporating C) sugar dissolving in water D) water boiling up as steam 23) The number of electrons in an iron ion, Fe2, is A) 24. B) 28. C) 26. D) 56

Explanation / Answer

(12) ------(C)

(13) ------(B)

(14) ------(C)

(15) ------(D)

(16) Balanced reaction

2C6H6 + 15 O2 -----> 12CO2 + 6H2O

Coefficient of oxygen is 15

(17) (C)

3O2 ------2O3

Coefficient of oxygen (O2) is 3

(18) (A)

(19) (C)

Mass of CH4 = 64.0 g , Molar mass of CH4 = 16 g/mol

No of moles of CH4 = 64.0 g / 16 g/mol = 4.0 mol

From reaction, 1 mol of CH4 reacts with 2 mol of O2, therefore 4.0 mol of CH4 will react with 2*4.0 mol = 8.0 mol of O2

(20) (C) nitrogen in dry air is 78%

(21)(B)

(10 g / 1000 g)*100 =1%

(22) (A)

(23) (A)

Atomic number - 2 = 26-2 = 24

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