<span>Errors can come from various sources: the obtainer of the data, the measuring instrument, the setting and etc. Errors are what makes your measurement invalid and unreliable. There are two types of error which is called the systematic error and the random error. Each error has different sources. Words that were mentioned –invalid and unreliable are very important key aspects to determine that your measure is truly accurate and consistent. Some would recommend using the mean method, doing three trials in measuring and getting their mean, in response to this problem.</span>
Answer:
Theoretical yield of vanadium = 1.6 moles
Explanation:
Moles of 
= 1.0 moles
Moles of 
= 4.0 moles
According to the given reaction:-
1 mole of react with 5 moles of
Moles of Ca available = 4.0 moles
Limiting reagent is the one which is present in small amount. Thus, Ca is limiting reagent. (4.0 < 5)
The formation of the product is governed by the limiting reagent. So,
5 moles of Ca on reaction forms 2 moles of V
1 mole of Ca on reaction for 2/5 mole of V
4.0 mole of Ca on reaction for 
mole of V
Moles of V = 1.6 moles
<u>Theoretical yield of vanadium = 1.6 moles</u>
The Equation of reaction
C + O2 === CO2
First Blank spot would be
---- 3.5moles of O2
2nd spot
Up.... 1mole of CO2
Down ---- 2moles of Oxygen atoms
3rd spot
Up... --- 22.4L of CO2(1mole of any gas at STP contains 22.4L)
Down---- 1mole of CO2
Final answer --- 3.5 x 1/2 x 22.4
=39.2L of CO2
When solid surfaces slide over each other, the kind of friction that occurs is called <u>Sliding Friction.</u>
