11th grade chemical reactions, acids and bases

Question 1

What is the mass of 4 mol of carbon dioxide (CO₂, Mr = 44), in g?

Answer g

Question 2

What mass of potassium hydroxide (KOH, Mr = 56) is needed to make 500 cm³ of 0.1 mol/dm³ solution, in g? Give 2 decimal places.

Answer g

Question 3

A student's yield is low because some crystals were left stuck to the filter paper. How could they improve it?

• A. rinse the filter paper with a little cold solvent to recover more product
• B. throw away the first crystals
• C. weigh the product while it is still wet
• D. use less of each reactant

Question 4

A sample contains 3.01 × 10²³ molecules. How many moles is this? (Avogadro constant = 6.02 × 10²³ per mol)

Answer mol

Question 5

Atom economy and percentage yield are different. Which statement is correct?

• A. Atom economy comes from the equation; yield comes from what you actually collect
• B. Yield comes from the equation only
• C. They are always equal
• D. Atom economy is measured with a balance

Question 6

How many moles are in 8 g of oxygen (O₂, Mr = 32)?

Answer mol

Question 7

0.02 mol of hydrochloric acid is in 200 cm³ of solution. What is the concentration, in mol/dm³?

Answer mol/dm³

Question 8

Atom economy: which statement is NOT true?

• A. Thermal decomposition of calcium carbonate has 100 % atom economy for calcium oxide.
• B. Atom economy is calculated from the balanced equation.
• C. Selling or using by-products makes a process less wasteful.
• D. Green chemistry aims to use reactions with high atom economy.

Question 9

What volume does 0.05 mol of ammonia gas occupy at room temperature and pressure, in dm³? (1 mol of any gas occupies 24 dm³ at RTP)

Answer dm³

Question 10

In a reaction, 1400 kJ is needed to break bonds and 1650 kJ is released when new bonds form. Is the reaction exothermic or endothermic?

• A. exothermic
• B. endothermic

Question 11

What volume does 0.5 g of hydrogen (H₂, Mr = 2) occupy at RTP, in dm³? (1 mol of gas = 24 dm³)

Answer dm³

Question 12

CaCO₃ → CaO + CO₂ (Mr: CaCO₃ = 100, CaO = 56). 25 g of calcium carbonate was heated and 11.2 g of calcium oxide was collected. What is the percentage yield? Give 1 decimal place.

Answer %

Question 13

N₂ + 3H₂ → 2NH₃. Bond energies (kJ/mol): N≡N 945, H–H 436, N–H 391. Calculate the energy change, in kJ/mol.

Answer kJ/mol

Question 14

How many moles of sodium hydroxide are in 25 cm³ of a 0.2 mol/dm³ solution?

Answer mol

Question 15

In an exothermic reaction, how do the energies of bonds broken and bonds made compare?

• A. more energy is released making bonds than is taken in breaking bonds
• B. breaking bonds releases more energy
• C. no bonds are made
• D. they are always equal

Question 16

CH₄ + H₂O → CO + 3H₂. The useful product is hydrogen (Mr 2). Relative masses of reactants: CH₄ = 16, H₂O = 18. What is the atom economy? Give 1 decimal place.

Answer %