General Chemistry Answers

Only two gallium isotopes are naturally occurring, 69Ga (mass = 68.9256 amu) and 71Ga (mass = 70.9247 amu). The atomic mass of gallium is 69.72. What percent of the gallium atoms (% abundance) is the heavier isotope?

[1] 36 %

[2] 38 %

[3] 40 %

[4] 59 %

[5] 61 % 

A bottle containing a greenish substance was labelled ferric chlorate. The material in this bottle is made up of:

[1] Fe2+ and ClO3 2- ions.

[2] Fe3+ and ClO2 - ions.

[3] Fe3+ and ClO3 - ions.

[4] Fe2+ and ClO4 - ions.

[5] F + and ClO2 - ions.

Which one of the following pairs are isotopes?

[1] O2 and O3

[2] 3517Cl and 3717Cl

[3] I2 (g) and I2 (s)

[4] Mg2+ and Ne

[5] F + and F-

A 5.2 cm3 of a metal is found to weigh 46.6 g on a three-decimal balance. What is the density of the metal, expressed to the proper number of significant figures?

[1] 9 g/cm3 [2] 9.0 g/cm3

[3] 8.96 g/cm3

[4] 0.11 g/cm3

[5] 0.112 g/cm3 

Which one of the statements below about mixtures is correct?

[1] The different substances in a mixture are always in a definite proportion to each other. [2] A mixture is made up of elements that are chemically combined.

[3] A mixture must contain at least two different substances.

[4] It is extremely difficult to separate a mixture into different substances.

[5] A mixture is always homogeneous

Mark eats a pastry that has 155 kilocalories. How many Joules of energy is this? (1 calorie = 4.184 Joules, 1 kilocalorie = 1000 calories)

Kevin places 175.5 g of solid aluminum into a pot and places it on the stove. He turns on the fire, causing it to melt. If the ΔHfus of aluminum is 405 J/g and the ΔHvap is 16700 J/g, how much energy did the aluminum gain?

You have 25 mL of an aqueous HCl solution in a conical flask. By titration (with a pH meter), 10 mL of 0.4 M NaOH is needed to neutralise the solution. (a) What pH reading will the neutralised solution give? [1 mark] (b) What is the molar concentration of the aqueous HCl solution (to 2 d.p.)? [3 marks]

(a) Draw the Lewis structures for each of the following: (i) NaOH (ii) NH4Cl (iii) CHCl3 [6 marks] (b) State the ground state electronic configurations of magnesium (Mg) atom and the chloride anion (Cl- ) [2 marks]

(a) Draw the Lewis structures for each of the following: (i) NaOH (ii) NH4Cl (iii) CHCl3 [6 marks] (b) State the ground state electronic configurations of magnesium (Mg) atom and the chloride anion (Cl- ) [2 marks]