Cobalt is comprised of 27 protons, 33 neutrons, and 27 electrons
Its a change in state of solid to liquid
the reason is that in a solid state the molecules have little kinetic energy to move and so they have restricted movement and so it remains solid
once heat is applied the molecules gain enough energy to move and so they turn into a liquid and move according to the laws of physics
hope that helps
For which of the following activities might you want to hire a chemist?
Answer: D. testing a rock sample for gold content
Which of the following procedures involves a physical change in one of the substances?
Answer: C. separating a salt solution by evaporating the water
Answer:
C is the excess reactant.
Explanation:
Reaction is C + O2 --> CO2
1mol of C required to react with 1mol O2
Therefore 15 - 10 = 5moles of C will be in excess
Answer:
3 × 10⁴ kJ
Explanation:
Step 1: Write the balanced thermochemical equation
C₃H₈(g) + 5 O₂(g) ⟶ 3 CO₂(g) + 4 H₂O(g) ΔH = -2220 kJ
Step 2: Calculate the moles corresponding to 865.9 g of H₂O
The molar mass of H₂O is 18.02 g/mol.
865.9 g × 1 mol/18.02 g = 48.05 mol
Step 3: Calculate the heat produced when 48.05 moles of H₂O are produced
According to the thermochemical equation, 2220 kJ of heat are evolved when 4 moles of H₂O are produced.
48.05 mol × 2220 kJ/4 mol = 2.667 × 10⁴ kJ ≈ 3 × 10⁴ kJ
