Chemical Reactions & Reactivity
What type of reaction is: Metal + Oxygen → Metal Oxide?
A: Combination/Synthesis
Which three colours are human cone receptors most sensitive to?
A: Red, Green, Blue
Put these EM waves in order of increasing frequency: , X-rays, visible, γ-rays?
A: Visible < X-rays < γ-rays
Which is a good conductor: wood, plastic, metal, or air?
A: Metal
What is an ore?
A: Rock containing enough metal for economical extraction.
In M + HX → MX + H₂, what is HX?
A: An acid
When red and blue cones are equally stimulated, what colour is perceived?
magenta
Complete the wave speed equation: v =
f x λ
In Ohm's Law, V =
IR
How is aluminium extracted from bauxite?
Electrolysis of molten aluminium oxide.
In the displacement reaction: M + mX → MX + m
How do M and m differ in reactivity?
M is a more reactive metal
Green objects under red+blue LED lamps appear black. Why?
A: They absorb red/blue light → no light reflected.
If light wavelength ↑ in vacuum, frequency ______.
A: Decreases
If resistance ↑ at constant voltage, current ______.
A: Decreases
Name 3 metals are commonly found native (elemental)?
A: Gold, Silver, Platinum,
Tin reacts with acid but not steam; Lithium reacts with cold water; Manganese reacts with steam but not cold water. Order their reactivity.
A: Lithium > Manganese > Tin
Mixing cyan and yellow pigments under white light gives which colour?
Green
Calculate frequency of a 500m-wavelength radio wave (c = 3×10⁸ m/s).
A: 600 kHz (f = c/λ = 3e8/500 = 600,000 Hz)
Two 6Ω resistors in parallel on a 12V circuit. Total current?
A: 4A (Rₜₒₜ = 3Ω; I = V/R = 12/3 = 4A)
Why was aluminium precious in 1850 but common today?
Electrolysis (Hall-Héroult, 1886) enabled mass production.
Why can carbon reduce iron oxide (Fe₂O₃ + 3C → 4Fe + 3CO₂) but not aluminium oxide?
A: Aluminium is above carbon in the reactivity series; carbon isn't strong enough to displace it.
Why does a blue object appear black under red light?
A: It absorbs red light → no light reflected.
Ultraviolet (UV) waves can cause sunburn, while visible light from the same Sun does not. What property of UV waves explains this?
A: Higher frequency / more energy
A 3Ω and 6Ω resistor in parallel with a 12V battery. How much current is being drawn from the battery?
(12/3) + (12/6) = 4 + 2 = 6A
Explain why carbon reduces iron oxide but not magnesium oxide.
A: Magnesium is above carbon in reactivity series; carbon can't displace it.