Homework 30
- Page ID
- 28945
1.35
A household receives a $125 electricity bill. The cost of electricity is $0.150 /kWh. How much energy, in joules (J), did the household use?
Solution:
Step 1: You must first multiply the total cost of the bill ($125) by 1 kWh and then divide that answer by the cost of each kW ($0.150 kWh). You should end up with an equation that looks like this:
\[($125)\times \dfrac{1\;kWh}{0.150\;kWh}\]
Step 2: Once you do this math, then you should receive the answer of 833.33 kWh. This is the number of kWh used during the billing cycle.
Step 3: Next, you will then take your solution found during step 1 and multiply it by \(\frac{1}{2.78\times 10^{-7}}\) in order to convert kWh to kWh/J. You should have the equation:
\[(833.33)\times \dfrac{1}{2.78\cdot 10^{-7}}\]
Step 4: After completing step 3, you should receive an answer of \[3.0 \times 10^{9} J\]
Step 5: YOU ARE FINISHED!
2.45
Classify each substance as a pure substance or a mixture. If it is a pure substance, classify it as an element or compound. If it is a mixture, classify it as homogenous or heterogeneous.
- tears
- lithium hydroxide
- gold
- bowl of chili
Solution:
- homogeneous mixture
- pure compound
- pure element
- heterogeneous mixture
Step 1: You must know the difference between a:
- pure substance - A substance that is made up of only one type of atom or molecule.
- mixture - A material system made up of two or more different substances that are mixed but not combined together chemically.
Step 2: You must know the difference between:
- element - Cannot be broken down into simpler substances.
- compound - Substance formed when two or more chemical elements are bonded together chemically and can be broken down into simpler substances.
- homogeneous - Mixture that has a uniform composition and properties throughout (cannot see ingredients)
- heterogeneous - Mixture that remains physically separated throughout (can see ingredients)
Step 3: Label either pure substance or mixture
Step 4: Label each pure substance as either an element or compound and each mixture as either homogeneous or heterogeneous.
Step 5: YOU ARE FINISHED!