Question 1.1 [2 marks]
To find the molecular formula from the empirical formula, we first determine the molar mass of the empirical formula, Mg₃Si₂H₃O₈.
Calculating the molar mass:
- Molar mass of Mg = 24.31 g/mol
- Molar mass of Si = 28.09 g/mol
- Molar mass of H = 1.01 g/mol
- Molar mass of O = 16.00 g/mol
\[ \text{Molar mass of } Mg_3Si_2H_3O_8 = (3 \times 24.31) + (2 \times 28.09) + (3 \times 1.01) + (8 \times 16.00) \] \[ = 72.93 + 56.18 + 3.03 + 128.00 \] \[ = 260.14 \text{ g/mol} \]
Now, divide the molar mass of the compound (520.8 g/mol) by the molar mass of the empirical formula (260.14 g/mol):
\[ \frac{520.8}{260.14} \approx 2 \]
Thus, the molecular formula is obtained by multiplying the subscripts in the empirical formula by 2:
\[ (2 \times Mg_3Si_2H_3O_8) = Mg_6Si_4H_6O_{16} \]
Answer: B. Mg₆Si₄H₆O₁₆
Question 1.2 [2 marks]
Bromothymol blue is a pH indicator that changes color over a certain pH range. It is typically used in titrations involving strong acids and strong bases, as it has a clear transition in this scenario.
Answer: D. Strong base and strong acid
Question 1.3 [2 marks]
For an exothermic reaction, the change in enthalpy (ΔH) is negative, indicating that energy is released in the form of heat. In addition, the products of the reaction will have less potential energy than the reactants.
Answer: B. ΔH is negative and the products have less potential energy than the reactants.
Question 1.4 [2 marks]
A standard solution is defined as a solution with a known concentration, typically used in titrations or other quantitative analyses. It does not have to contain one mole of solute per dm³ or always be made up to 1 dm³.
Answer: C. is a solution of which the concentration is precisely known.
Question 1.5 [2 marks]
This question seems to refer to an accompanying figure showing a potential energy diagram, which is not provided in your text. However, this potential energy diagram typically illustrates the energy changes throughout a chemical reaction, showing the potential energy of reactants and products, as well as the activation energy.
If you could provide specific information or questions related to the diagram, I'd be glad to help!
1 answer