Answer:
beryllium iodide has a molar mass of 262.821 g mol−1 , which means that 1 mole of beryllium iodide has a mass of 262.821 g . To find the mass of 0.02 moles of beryllium iodide, simply multiply the number of moles by the molar mass in conversion factor form.
Explanation:
A) c = 3 x 10^8 m/s
f = 7.15 x 10^14 Hz
c = λ x f (=) λ = 3 x 10^8 / 7.15 x 10^14 = 4.19 x 10^-7 m = 419.6 nm
B) E = h f
H = Planck's constant = 6.63 x 10^-34 J/s
E = 6.63 x 10^-34 x 7.15 x 10^14 = 4.74 x 10^-19 J
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Rubber, because it doesn’t conduct heat and it is a good insulator
Answer:
The number of stamps and cards Maggie has left if she gives 45 stamps to a friend is 183
Explanation:
If Maggie gives 45 stamps to a friend, you must calculate the number of stamps and cards she has left.
You know Maggie has 4 folders with 30 stamps in each folder. So the number of stamps she owns is calculated as:
4 folders*30 stamps in each folder= 120 stamps
If Maggie gives 45 stamps to a friend, then the number of stamps she has left will be calculated as the difference (the subtraction) between the stamps she owned and the ones she gives away:
120 stamps - 45 stamps= 75 stamps
On the other hand, she has 3 binders with 36 baseball cards in each binder. So the number of cards she owns is calculated as:
3 binders * 36 baseball cards in each binders= 108 baseball cards
The number of stamps and cards you have left is calculated as:
75 stamps + 108 baseball cards= 183
<em><u>The number of stamps and cards Maggie has left if she gives 45 stamps to a friend is 183</u></em>
Answer:
magnesium metal melts = physical change
magnesium metal ignites = chemical change
Explanation:
<em>Physical changes</em> are those in which the identity of the subtance <u>remains unaltered</u>. No new compounds are formed. They involve generally changes in <u>agreggation states of matter</u>: solid, liquid or gas. The first experiment, in which magnesium metal melts is a physical change because it only changes the state of matter, from solid to liquid, but it is still magnesium metal.
Conversely, <em>chemical changes</em> involve atoms combinations to form new compounds. The second experiment, in which magnesium metal ignites, is a chemical change. After the change, magnesium metal is no longer the metal but a metal oxide.
