CIE iGCSE Co-Ordinated Science C3.1 Formulas Exam Style Questions Paper 2
▶️ Answer/Explanation
In equation B, the left side has \(4\) oxygen atoms (from \(Fe_3O_4\)) but the right side shows only \(2\) oxygen atoms (in \(2H_2O\)).
Since \(4 \neq 2\), oxygen atoms are not conserved, so this equation is not correctly balanced.
✅ Answer: (B)
Since \(4 \neq 2\), oxygen atoms are not conserved, so this equation is not correctly balanced.
✅ Answer: (B)
▶️ Answer/Explanation
From \(Na_3PO_4\), the phosphate ion must have a charge of \(3-\), giving \(PO_4^{3-}\).
From \(Al_2(SO_4)_3\), balancing charges shows the aluminium ion is \(Al^{3+}\).
Combining \(Al^{3+}\) with \(PO_4^{3-}\) requires a 1:1 ratio, since the charges already balance, giving \(AlPO_4\).
✅ Answer: (A)
From \(Al_2(SO_4)_3\), balancing charges shows the aluminium ion is \(Al^{3+}\).
Combining \(Al^{3+}\) with \(PO_4^{3-}\) requires a 1:1 ratio, since the charges already balance, giving \(AlPO_4\).
✅ Answer: (A)
▶️ Answer/Explanation
To balance the equation: Cu is balanced (1 each). On the right, there are 2 nitrate groups in Cu(NO₃)₂ and s nitrate groups in NO₂, requiring q = s + 2 for nitrogen. For oxygen: left has 3q, right has 6 + 2s + t. For hydrogen: left has q, right has 2t, so q = 2t. Testing values, q = 4, s = 2, t = 2 balances the equation: Cu + 4HNO₃ → Cu(NO₃)₂ + 2NO₂ + 2H₂O.
✅ Answer: (D)
✅ Answer: (D)
Question
The equation for the reaction of sodium with water is shown.
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
Which mass of sodium produces 30 cm3 of hydrogen?
(A) 0.0288 g (B) 0.0575 g (C) 28.8 g (D) 57.5 g
▶️Answer/Explanation
Ans: B
Question
The equation for the combustion of magnesium is shown.
2Mg + O2 → MgO
What is the mass of magnesium oxide formed from 12 g of magnesium?
(A) 20g (B) 24g (C) 40g (D) 80g
▶️Answer/Explanation
Ans : BA