Three repeated demonstrations with equal samples of a group 1 metal collect hydrogen volumes of 47, 49 and 48 cm³. A separate run collects 31 cm³ after the gas tube becomes loose.
.1
Calculate the mean volume from the three valid repeated demonstrations.
[3 marks]
.2
Explain why the low run cannot show that the metal was less reactive.
[2 marks]
4 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A student says: "Crude oil is a compound. Fractional distillation breaks its molecules into simpler hydrocarbons. Each fraction contains one pure substance."
Evaluate each part of this explanation.
[4 marks]
6 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
A student gives this explanation: "An exothermic reaction has weak product bonds. Breaking the reactant bonds releases energy, and activation energy is the same as overall energy change."
Evaluate the explanation using bond breaking, bond formation and reaction profiles.
[6 marks]
4 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A company claims that because its hydrocarbon fuel burns with no smoke it causes neither acid rain nor climate change. The fuel contains small amounts of sulfur and is burned at high temperature in air.
Evaluate the claim using the possible gaseous products.
[4 marks]
4 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A reaction uses the same solution concentration at 20 °C and 35 °C. A student explains the faster reaction at 35 °C by saying particles are larger and the activation energy has decreased.
