Answer:
We need 1.1 grams of Mg
Explanation:
Step 1: Data given
Volume of water = 78 mL
Initial temperature = 29 °C
Final temperature = 78 °C
The standard heats of formation
−285.8 kJ/mol H2O(l)
−924.54 kJ/mol Mg(OH)2(s)
Step 2: The equation
The heat is produced by the following reaction:
Mg(s)+2H2O(l)→Mg(OH)2(s)+H2(g)
Step 3: Calculate the mass of Mg needed
Using the standard heats of formation:
−285.8 kJ/mol H2O(l)
−924.54 kJ/mol Mg(OH)2(s)
Mg(s) + 2 H2O(l) → Mg(OH)2(s) + H2(g)
−924.54 kJ − (2 * −285.8 kJ) = −352.94 kJ/mol Mg
(4.184 J/g·°C) * (78 g) * (78 - 29)°C = 15991.248 J required
(15991.248 J) / (352940 J/mol Mg) * (24.3 g Mg/mol) = 1.1 g Mg
We need 1.1 grams of Mg
Answer:
The cost of electricity for 100 W power bulb = $ 32.85
Cost of electricity for 0.025 W fluorescent bulb = $ 8.2125
Explanation:
Cost of electricity = $ 0.18 per KW-H
Time = 5 hour per day
Bulb power = 100 W = 0.1 KW
Fluorescent bulb power = 25 W = 0.025 KW
(a) Cost of electricity for 100 W power bulb
0.1 × 5 × 365 × 0.18 = $ 32.85
(b) Cost of electricity for 0.025 W fluorescent bulb
0.025 × 5 × 365 × 0.18 = $ 8.2125
Therefore the cost of electricity for 100 W power bulb = $ 32.85
Cost of electricity for 0.025 W fluorescent bulb = $ 8.2125
During photosynthesis, what gas do plants release - oxygen
