Answer:
About 1.254 moles
Explanation:
The first step is to find the molar mass of selenium. If you take a look at a periodic table, you will find that there is a little number underneath that says something around 78.96 g/mol. Dividing 99 grams by this number, you get about 1.254 moles of Se. Hope this helps!
O B. The total mass of the reactants equals the total mass of the
products.
Answer:
Physical properties: how soft a blanket it, how hard bread is, what color leaves are, what bleach smells like.
Chemical change: burning wood, rotting food, digestion, rusting of a nail.
Physical change: mixing salt and sugar, tearing a piece of paper, melting ice, chopping wood.
Explanation:
Physical properties are properties that are measurable.
Chemical change is when substances combine (fire and wood make burning wood) to make another substance. They aren't reversible. If you were to melt ice, you could refreeze it, you can't unburn wood.
Physical change is something that alters the form of the substance but not the chemical composition.
Hope this helps!
Explanation:
Expression for the 
speed is as follows.
where, = root mean square speed
k = Boltzmann constant
T = temperature
M = molecular mass
As the molecular weight of oxygen is 0.031 kg/mol and R = 8.314 J/mol K. Hence, we will calculate the value of as follows.
= 
= 498.5 m/s
Hence, for oxygen atom is 498.5 m/s.
For nitrogen atom, the molecular weight is 0.028 kg/mol. Hence, we will calculate its speed as follows.
= 
= 524.5 m/s
Therefore, speed for nitrogen is 524.5 m/s.
What is the relationship between wavelength, frequency and energy? The energy of a wave is directly proportional to its frequency, but inversely proportional to its wavelength. In other words, the greater the energy, the larger the frequency and the shorter (smaller) the wavelength.
