Question
Why does the melting point of the elements decrease down group 1?
A. Atomic mass increases
B. Number of electrons increases
C. Radius of metal ion increases
D. First ionization energy decreases
▶️Answer/Explanation
Markscheme: C
Question
In which molecule does the central atom have an incomplete octet of electrons?
A. \(\rm H_2Se\)
B. \(\rm PH_3\)
C. \(\rm OF_2\)
D. \(\rm BF_3\)
▶️Answer/Explanation
Markscheme: D
Question
The enthalpy of formation of ammonia gas is -46kJ \(mol^{-1}\)
\(N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)\)
What is the energy released, in KJ, in the reaction?
A. 23
B. 46
C. 69
D. 92
▶️Answer/Explanation
Markscheme: D
Question
A sample of calcium carbonate reacts with excess hydrochloric acid in a beaker. The solid line shows how the mass of the beaker changes with time.
Which dashed line represents the results obtained when the acid concentration is doubled?
Answer/Explanation
Ans: B
Question
What is the coefficient of $\mathrm{HCl}$ (aq) when the equation is balanced using the smallest possible whole numbers?
$$
\ldots \mathrm{CuO}(\mathrm{s})+\ldots \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{CuCl}_2(\mathrm{aq})+\ldots \mathrm{H}_2 \mathrm{O}(\mathrm{l})
$$
A. $1$
B. $2$
C. $3$
D. $4$
Answer/Explanation
Solution:B