Topical Test Chapter 1

Which atom has the smallest number of neutrons?

• carbon-12

• nitrogen-14

• oxygen-16

• fluorine-19

Identify the species that has the same number of electrons and neutrons.

•  $1_H$  

•  $14_C$  

•  $19_{F^-}$  

•  $14_{C^{2+}}$  

Which of these represent an element?

i Ne

ii Cl₂

iii O₃

• i and ii

• ii and iii

• all of above

A calcium atom is 3.33 times the mass of a carbon atom. What is the atomic mass of calcium?

• 33

• 40

• 38

• 12

The mass spectrum of Ne shows three peaks at masses 20, 21, and 22 amu. The heights of the peaks are in the ratio 114:0.2:11.2. The average atomic mass of Ne is

• $\frac{\left(20\times114\right)+\left(21\times11.2\right)+\left(22\times0.2\right)}{114+0.2+11.2}$

• $\frac{\left(20\times114\right)+\left(21\times0.2\right)+\left(22\times11.2\right)}{20+21+22}$

• $\frac{\left(20\times114\right)+\left(21\times0.2\right)+\left(22\times11.2\right)}{114+0.2+11.2}$

• $\frac{\left(20\times114\right)+\left(22\times11.2\right)}{114+11.2}$

A solution contains 28% sulphuric acid by mass. This means that

• 1dm³ of solution contains 28g of sulphuric acid

• 1dm³ of solution has a mass of 28g

• 100g of solution contains 28g of sulphuric acid

• 100g of solution contains 28% sulphuric

The number of oxygen atoms in 2.50 mol K₂Cr₂O₇ is

• 6.02 x 10²³

• 1.20 x 10²⁴

• 1.55 x 10²⁵

• 1.05 x 10²⁵

What is the percent by mass of Na₂CO₃ in a 1.0 molal aqueous solution?

• 8.5

• 9.6

• 10.2

• 12.4

A 45% by mass of glucose (C₆H₁₂O₆) solution contains 70g of water. What is the mass of glucose in the solution?

• 57.3

• 53.3

• 35.7

• 17.5

How many nitrogen atoms are present in 28 dm³ of nitrogen gas at s.t.p?

(Molar volume of gas = 22.4 dm³ at s.t.p ; Avogadro constant = 6.02 x 10²³)

• 1.5 x 10²³ atoms

• 7.5 x 10²³ atoms

• 1.5 x 10²⁴ atoms

• 3.0 x 10²⁴ atoms