The question is incomplete, here is the complete question:
Consider the following reaction: 
In the first 15.0 s of the reaction, 1.9×10⁻² mol of O₂ is produced in a reaction vessel with a volume of 0.480 L . What is the average rate of the reaction over this time interval?
<u>Answer:</u> The average rate of appearance of oxygen gas is 
<u>Explanation:</u>
We are given:
Moles of oxygen gas = 
Volume of solution = 0.480 L
Molarity is calculated by using the equation:

So, 
The given chemical reaction follows:

The average rate of the reaction for appearance of
is given as:
![\text{Average rate of appearance of }O_2=\frac{\Delta [O_2]}{\Delta t}](https://tex.z-dn.net/?f=%5Ctext%7BAverage%20rate%20of%20appearance%20of%20%7DO_2%3D%5Cfrac%7B%5CDelta%20%5BO_2%5D%7D%7B%5CDelta%20t%7D)
Or,

where,
= final concentration of oxygen gas = 0.0396 M
= initial concentration of oxygen gas = 0 M
= final time = 15.0 s
= initial time = 0 s
Putting values in above equation, we get:

Hence, the average rate of appearance of oxygen gas is 
<span>Magnetic fields in certain materials (most commonly metals) are created due to moving electrons within these materials, which create an electric current.The distribution of electrons in these metals is uneven, resulting in an irregular rotation and lots of movement that then creates two magnetic poles (a north and south pole). When these poles align and face the same direction, they create a magnetic field.</span>
The function of the soap is to help wash off the oils. Because oil is hydrophobic, and soap is made of molecules that are both hydrophobic and hydrophilic, the soap molecules can connect to both oil and water. When the soap is combined with water and oil, it causes the oil to form small drops that can easily be washed off.
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Answer is: sodium fluoride NaF.
Sodium fluoride hydrolyse on strong base sodium hydroxide (NaOH) and weak acid hydrofluoric acid (HF), so water solution has pH greater that seven ant it is basic. Other salts have neutral or acidic pH value in water, because they hydrolyse on strong acid and weak or strong base.
Answer:
She gave them bottles with labels showing the brands
Explanation:
the teens could have been biased due to knowing the brand. It would have been more reliable if the label was covered or removed.