In an experiement things that are changing are called variables.
Answer:
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Explanation:</h2>
<em><u>The statement “the scientific process is open ended” means: Would an element with 7 valence electrons be more or less reactive than an element with 3 valence electrons? Element 1 is a hard dark-red solid</u></em>
Answer:
A) involves changes in temperature
Explanation:
The figure is missing, but I assume that the region marked X represents the region in common between Gay-Lussac's law and Charle's Law.
Gay-Lussac's law states that:
"For an ideal gas kept at constant volume, the pressure of the gas is directly proportional to its absolute temperature"
Mathematically, it can be written as

where p is the pressure of the gas and T its absolute temperature.
Charle's Law states that:
"For an ideal gas kept at constant pressure, the volume of the gas is directly proportional to its absolute temperature"
Mathematically, it can be written as

where V is the volume of the gas and T its absolute temperature.
By looking at the two descriptions of the law, we see immediately that the property that they have in common is
A) involves changes in temperature
Since the temperature is NOT kept constant in the two laws.
Answer: 2.88×
atoms 
Explanation: First, using stoichiometry, we must convert this from grams to moles, then from moles to atoms.
1. For the first step, we should also look at the periodic table to find the molar mass of the compound, then use that as the denominator.

2. Now that it is converted to moles, we must convert it to atoms by multiplying it by Avogadro's number.

With this information, we know that there are
total atoms in 0.680 grams
.
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Answer:
2) Add a solution of NaBr
Explanation:
Lead (II) bromide is an inorganic powdery substance that has a solubility in water of 0.973 g/100 mL at 20°C. It is insoluble in alcohol but is soluble in alkali, ammonia, NaBr, and KBr
PbBr₂ is slightly soluble in ammonia, and it reacts with NaOH to produce Pb(OH)₂ and NaBr
Therefore, the best solution for dissolving PbBr₂(s) is NaBr