Question

Multiple Choice Please answer all parts of this question.

Question 26 with 4 parts:

a. Calculate the mass (in grams) of 10.7 moles of He.

  

2.67

   

6.02 ´10²³

  

6.44 ´10²⁴

  

14.7

b. The correct name for P₃O₇ is:

  

triphosphorus hexaoxide

  

triphosphorus heptaoxide

  

phosphorus(II) oxide

  

phosphorus(V) oxide

c. A 86.17-g sample of NaCl is dissolved in 250.0 mL of solution. Calculate the molarity of this solution.

  

5.898 M

  

1.475 M

  

344.7 M

  

7.131 M

d. Use the following choices to classify the reaction given below (more than one choice may apply):

2Na(s) + H₂(g) ® 2NaH(s)

a. oxidation-reduction

b. combustion

c. synthesis

d. decomposition

Answer choices:  

b & c

  

c & d

  

a & c

  

a & b

Answer 1

(a)

Moles of He= mass of He/molecular weight of He =10.7 mol*4 g/mol=42.8 g.

But the options doesnot contains the obtained answer.

If mass of He is 10.7, then moles =10.7/4=2.67 mol

(b)

Molecular name of P₃O₇ is Triphosphorus septoxide.

(c) molarity=moles of NaCl /Volume of solution

Moles of NaC l =86.17 g/58.5 g/mol=1.472 mol.

Volume in litres=0.25 L

Molarity=1.42 mol/0.25 L=5.88 mol/L.

So, A is the correct option.

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2NaH(s) ----> 2Na(s)+ H₂(g)

Na in NaH is reduced, and NaH is the oxidizing agent.

H in NaH is oxidized, and NaH is also the reducing agent.

2NaH(s) ----------> 2Na(s) + H₂(g) .It is a decomposition reaction.

Thus, 3 option (a and c ) is the correct answer