Quantitative chemistry

Number of moles in 12.4 t of NaNO₃ ÷ number of moles in 12.4 t of NaCl =

• 7.0

• 0.69

• 49.1

Two students complete the synthesis of paracetamol from 4-aminophenol as shown by the equation on the picture.

Both students react 2 moles of 4-aminophenol with excess ethanoyl chloride.

Student 1 makes 1.5 moles of paracetamol. Student 2 makes 220 g of paracetamol.

Which student has the better percentage yield?

(Don't worry about the complicated names, use the molecular formulas.)

• Student 1, 76 %

• Student 1, 75 %

• Student 2, 74 %

• Student 2, 73 %

According to Avogadro’s Law, as long as the pressure and temperature are kept the same, equal volumes of gases contain equal numbers of moles of gas. Under standard temperature and pressure (273 K and 101,325 Pa) 1 mole of any gas has a volume of 22.4 dm³. Use Avogadro’s law to find out which gas syringe contain identical numbers of moles of gas as the syringe A (on the picture).

• Syringe F

• Syringe G

• Syringe H

• Syringe I

• Syringe J

In the following equation, what is the molar ratio between hydrochloric acid and copper(II) oxide?

2 HCl + CuO → CuCl₂ + H₂O

• 1 : 2

• 2 : 1

• 1 : 1

What is the empirical formula of octane C₈H₁₈?

• CH₂

• C₄H₉

• C₈H₁₈

In an experiment, the actual yield is 8.4 g but the theoretical yield is 17.0 g. what is the percentage yield?

• 24.7 %

• 50.6 %

• 49.4 %

When the equation below is balanced, what is the coefficient for oxygen?

__C₂H₂(g) + __O₂(g) → __ CO₂(g) + __ H₂O(g)

• 2

• 3

• 4

• 5

Ethyne, C₂H₂, reacts with oxygen according to the equation below. What volume of oxygen (in dm³) reacts with 0.40 dm³ of C₂H₂? (STP)

2 C₂H₂(g) + 5 O₂(g) → 4 CO₂(g) + 2 H₂O(g)

• 0.40

• 0.80

• 1.0

• 2.0

How many oxygen atoms are present in 0.0500 mol carbon dioxide?

• 3.01×10²²

• 6.02×10²²

• 6.02×10²³

• 1.20×10²⁴

What mass (g) of potassium hydroxide (KOH) is needed to make up 500 cm³ of a solution of concentration 0.2 mol.dm^-3?

• 2.8

• 11.2

• 5.6

• 0.56