<u>Answer:</u> The true statements are 
for an endothermic reaction is positive, a combustion reaction is exothermic and when energy is transferred as heat from the system to the surroundings, is negative.
<u>Explanation:</u>
There are 2 types of chemical reactions categorized into heat change:
- <u>Endothermic reactions:</u> These reactions are defined as the reactions in which energy is absorbed by the system from the surroundings. The for these reactions is always positive. For Example: Changing of water into water vapor.
- <u>Exothermic reactions:</u> These reactions are defined as the reactions in which energy is released by the system to the surroundings. The for these reactions is always negative. For Example: Combustion reactions.
Combustion reactions are defined as the reactions in which a hydrocarbon reacts with oxygen gas to produce carbon dioxide and water. Heat is released during these reactions. Thus, it is considered as exothermic reactions.
Hence, the true statements are for an endothermic reaction is positive, a combustion reaction is exothermic and when energy is transferred as heat from the system to the surroundings, is negative.
Answer: The first steps
Explanation: science
Answer:
133 g
Explanation:
Step 1: Write the balanced equation
2 Al(s) + 3 Br₂(l) ⇒ 2 AlBr₃(s)
Step 2: Calculate the moles corresponding to 15.0 g of Al
The molar mass of aluminum is 26.98 g/mol. The moles corresponding to 15.0 g of Al are:
Step 3: Calculate the moles of Br₂ that react with 0.556 moles of Al
The molar ratio of Al to Br₂ is 2:3. The moles of bromine that react with 0.556 moles of aluminum are:
Step 4: Calculate the mass corresponding to 0.834 moles of Br₂
The molar mass of bromine is 159.81 g/mol. The mass corresponding to 0.834 moles of Br₂ is:
The law of conservation of mass dictates that the total mass of reactants must be equal to the total mass of the products. Thus:
mass(MgO) = mass(Mg) + mass(O)
mass(MgO) = 24 + 16
mass(MgO) = 40 g
The third option is correct.
Answer:
Explanation:
Pascal(Pa) : It is the SI unit of pressure.It is equal to 1 Newton per meter square(Pa =
)
is the Unit of Force(Newton=N)
<u>Calculation,</u>
It is required to convert 
to 
only, Pa is same in both so no need to alter Pa.
1 m = 1000 mm (see the image)
And,
1 mm = 0.001 m
(Squaring both side)
So,
