Answer:
1. Exothermic.
2. -1598 kJ.
Explanation:
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1. In this case, according to the reaction, we can infer that 799 kJ of energy are evolved (given off, released) it means that the enthalpy of reaction is negative as the reactants have more energy than the products; which means this is an exothermic reaction.
2. Here, as we know that the enthalpy of reaction is -799 kJ/mol, we can compute the q-value as shown below, considering the reacted 2 moles of solid iron:
Which means that 1598 kJ of energy are evolved when 2 moles of solid iron react.
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Yasir wanted to study the relationship between sleep and room color. So he has done all the background study required on the topic and arrived at a hypothesis that people fall asleep more rapidly in a room painted in blue color than in a room painted yellow. Yasir inquired several people which color they like better -yellow or blue- and used their feedback to decide whether his hypothesis was correct. There was no experiment conducted to observe the effect of a room color on sleep and the variables to be tested in the experiment were not properly identified.
Therefore, the correct answer would be,
An experiment that directly tests the hypothesis
Variables to be tested by an experiment
1) Calcium carbonate contains 40.0% calcium by weight.
M(CaCO₃)=100.1 g/mol
M(Ca)=40.1 g/mol
w(Ca)=40.1/100.1=0.400 (40.0%)!
2) Mass fraction of this is excessive data.
3) The solution is:
m(Ca)=1.2 g
m(CaCO₃)=M(CaCO₃)*m(Ca)/M(Ca)
m(CaCO₃)=100.1g/mol*1.2g/40.1g/mol=3.0 g
Equation: 2K + S --> K2S
Chemical formula: K2S
swift to hear, slow to speak
Explanation:
