Question

1.The atomic mass unit is presently based on assigning a mass of exactly 12 amu to:

(a) an atom of carbon isotope ¹³C      (b) an atom of carbon isotope ¹²C     (c) all carbon atoms

(d) the average atomic mass of carbon

Which of the following samples contain the greatest number of oxygen atoms?

(a) 1mol H₂O (b) 3 x 10²³ molecules O₃    (c) 1mol CO₂   (d) 1mol CO

Approximately, how many oxygen molecules are in a 16.00 g sample of oxygen?

(a) 1 x 10²³    (b) 2 x 10²³    (c) 3 x 10²³    (d) 6 x 10²³     (e) 8 x 10²³   

The number of moles of nitric acid (HNO₃) present in 126.04 g of nitric acid is:

   (a) 1    (b) 2    (c) 0.5    (d) 1.5

Which one of the following is a correct expression for molarity?

   (a) mol solute/L solvent     (b) mol solute/L solution       (c) mol solvent/L solution

   (d) mol solution/L solvent

How many grams of potassium chloride are there in 100.0 ml of 1.50 M KCl ?

   (a) 11.2 g (b)112 g ( c) 1.12 g (d) None of these

Which statement is not true?

   (a) 1 mole of Na₂CO₃ contains same number of Na⁺ cations as CO₃^2- anions

   (b) 1 mole of Na₂CO₃ contains twice as many Na⁺ cations as CO₃^2- anions

   (c) 1 mole of Na₂CO₃ contains Na⁺ cations and CO₃^2- anions in the ratio 2:1

   (d) 1 mole of Na₂CO₃ contains twice the Avogadro number of Na⁺ cations

Which one of the following molecular formulas is not an empirical formula?

   (a) CHO     (b) C₂H₂O₃     (c) C₆H₉O₃       (d) C₁₂H₁₄O₃      (e) C₁₄H₁₂O₃

​Please help!!!

Answer 1

1.The atomic mass unit is presently based on assigning a mass of exactly 12 amu to:

Ans: (b) an atom of carbon isotope ¹²C

2. Which of the following samples contain the greatest number of oxygen atoms?

Ans: (a) 1mol H₂O (Oxygen atoms present is 5.35 x 10²³ atoms)

3. Approximately, how many oxygen molecules are in a 16.00 g sample of oxygen?

Ans: (c) 3 x 10²³

4. The number of moles of nitric acid (HNO₃) present in 126.04 g of nitric acid is:

Ans: (b) 2 (no. of moles = 126.04/63.02 = 2)

5. Which one of the following is a correct expression for molarity?

Ans: (a) mol solute/L solvent

6. How many grams of potassium chloride are there in 100.0 ml of 1.50 M KCl

Ans: (a) 11.2 g ( 0.15 x 74 = 11.2)

7. Which statement is not true?

Ans: (a) 1 mole of Na₂CO₃ contains same number of Na⁺ cations as CO₃^2- anions

8. Which one of the following molecular formulas is not an empirical formula?

Ans: (c) C₆H₉O3   (this can be represented as C2H3O)