Some Basic Concepts Of Chemistry Test 13

Result

Some Basic Concepts Of Chemistry Test 13

Score
-
out of -
Rank
-
out of -

TIME Taken - -

SHARING IS CARING

If our Website helped you a little, then kindly spread our voice using Social Networks. Spread our word to your readers, friends, teachers, students & all those close ones who deserve to know what you know now.

Weekly Quiz Competition

Question 1
1 / -0

The reference standard used for defining atomic mass is

A
H-1

B
C-12

C
C-13

D
C-14

Solution

C-12 is used as a standard unit for defining atomic mass unit.
Question 2
1 / -0

Atomic masses of elements are usually fractional because

A
These are mixtures of isotopes

B
They contain impurities of other atoms

C
They are mixtures of isobars

D
Atomic masses cannot be weighed accurately

Solution

Atomic masses are the average atomic masses of the mixture of isotopes and calculated on the basis of relative abundance, hence they are usually fractional.
Question 3
1 / -0

Oxygen occurs in nature as a mixture of isotopes ¹⁶O, ¹⁷O, and ¹⁸O having atomic masses of 15.995 u, 16.999 u and 17.999 u and relative abundance of 99.763%, 0.037% and 0.200% respectively. What is the average atomic mass of oxygen?

A
15.999 u

B
16.999 u

C
17.999 u

D
18.999 u

Solution

Atomic mass of oxygen
= 15.999 u
Question 4
1 / -0

For every one ³⁷Cl isotope there are three ³⁵Cl isotopes in a sample of chlorine. What will be the ayerage atomic mass of chlorine?

A
35

B
37

C
35.5

D
35.6

Solution

Atomic mass of chlorine =
Question 5
1 / -0

Carbon occurs in nature as a mixture of ¹²C and ¹³C. The average atomic mass of carbon is 12.011. What is the % abundance of ¹²C in nature?

A
88.9%

B
98.9%

C
89.9%

D
79.9%

Solution

Let % abundance of ¹²C = x
% abundance of ¹³C = 100 - x

2x + 1300 - 13x = 1201.1 ⇒ x = 98.9%
Thus, abundance of ¹²C is 98.9%.