Question

20) 20) Which of the following statements concerning a voltaic cell is FALSE A) At the anode a substance will lose electrons. B) A voltaic cell uses an oxidation-reduction reaction to produce electrical energy. C) The oxidation half reaction occurs at the cathode. D) The cell consists of two half cells. E) The anode and the cathode are separated by a salt bridge. - 21) The fluoride rinse in dental offices usually contains sodium fluoride, Sodium fluoride 2 1 can be prepared from the reaction between sodium metal and fluorine gas. Which one following properly represents the balanced chemical equation for this reaction A) 7Na(s) + F(g) Na7F($) B) 2 Na(s) + F2(g) → 2NaF(S) C) Na(s) + F2(g) NaF2($) D) Na(s) + F(g) NaF(s) E) 2Na(s) + F29) ► 2Na2F(5) 22) How is the reaction shown below best classified? Ca(s) + 2HCl(aq) +CaCl2(g) + H2(g) A) precipitation B) decomposition C) double-replacement D) combination E) single-replacement 23) 23) How is the reaction shown below best classified? 2NaCl(s) + F2(g) + 2NaF(s) + Cl2(g) A) combination B) double-replacement C) precipitation D) single-replacement E) decomposition 24) 24) What is the mass of a 0.150 mole sample of sulfur? A) 5.17 g C) 4.68 g D) 4.81 g E) 214 g 25) 25) A sample of sulfur contains 1.81 x 1024 atoms of sulfur. How many moles of sulfur does this represent? A) 0.333 mol B) 3.01 mol C) 1.09 mol D) 1.81 mol E) 1.77 mol

Answer 1

ANSWER:

1)- correct option is( c) because oxidation half-reaction occurs at anode.

2)- the correct option is(b) because this is correct balance equation

3)- this reaction is the example of single-replacement reaction so the correct option should be (e)

4)- this is also an example of single-replacement reaction. correct option is (d)

5)- n is given =0.150 mass of sulfur is 32 so we know tha n=w/m so w=n*m = 0.150*32= 4.8 w=4.8g so correct option should be (d)

6)- given atoms of sulfur 1.81 *10²⁴ convert it into moles we know that

1 mole of Sulphur= 6.022 x 10²³ atoms of Sulphur

so 1.81* 10²⁴/6.0222 * 10²³ = 0.3001 * 10 = 3.001moles

so the correct option is (b)