Chemical Properties of Metals (Reaction with O2, H2O, Acids) MCQs

Q1. What is the direction of the reaction in a word-equation?

• A.The arrowhead points towards the reactants
• B.The arrowhead points towards the products
• C.The arrowhead points in both directions
• D.There is no arrowhead

Answer: B. The arrowhead points towards the products

Going back to the NCERT chapter, The arrowhead points towards the products, showing the direction of the reaction. That fits the listed correct option directly - This shows the direction of the reaction. Quickly on the wrong ones: option A) 'The arrowhead points towards the reactants' fails since The arrowhead points towards the products; option C) 'The arrowhead points in both directions' is wrong because The arrowhead points in one direction, towards the products. Hence the answer is B) The arrowhead points towards the products.

Q2. Which equation correctly represents the reaction of Plaster of Paris with water (setting into a hard mass)?

• A.CaSO4·½H2O + 1½H2O → CaSO4·2H2O
• B.CaSO4·½H2O + ½H2O → CaSO4·2H2O
• C.CaSO4·2H2O → CaSO4·½H2O + 1½H2O
• D.CaSO4·½H2O → CaSO4 + ½H2O

Answer: A. CaSO4·½H2O + 1½H2O → CaSO4·2H2O

Q3. Which of the following is evidence that a chemical reaction has taken place?

• A.A change in colour, formation of a gas or precipitate, or a change in temperature
• B.Only a change in the shape of the container
• C.Only the passage of time
• D.The substances simply being mixed together

Answer: A. A change in colour, formation of a gas or precipitate, or a change in temperature