Answer:
A = 55
Explanation:
The atomic number is the number of protons also = the number of electrons, so basically we have 29 neutrons, 26 electrons and 26 protons. Anyway, it's asking the mass number which is the neutrons + the protons, so you just take 29+26 = 55
Answer:
Energy,
Explanation:
It is required to find the energy of an electromagnetic wave with a frequency of . The energy of a wave in terms of its frequency is given by :
= frequency of em wave
So, the energy of an electromagnetic wave is
Based on the balanced chemical reaction presented above, every mole of magnesium (Mg) yields one mole of diatomic hydrogen (H2). When converted to masses, every 24.3 grams of magnesium yields 2 grams of hydrogen.
From the given, there are 20 grams of magnesium available for the reaction. With this amount, the expected yield of hydrogen is 1.646 grams. To calculate the percent yield, divide the actual yield to the hypothetical yield.
*The case is impossible because the actual yield is greater than the theoretical yield.
If we assume that there had been a typographical error and that the actual yield is 0.7 grams instead of 1.7 grams, the percent yield becomes 42.5%. Thus, the answer is letter E.
Answer:
1 mol of K
Explanation:
The reaction is: 2K + Cl₂ → 2KCl
2 moles of potassium react with 1 mol of chlorine to make the salt, potassium chloride
If you see the stoichiometry from reactants, 2 moles of K need 1 mol of Cl₂ to react, so 1 mol of Cl₂ needs 2 moles of K, to react too.
We can make a rule of three, to reach the answer:
1 mol of Cl₂ needs 2 moles of K to react
Then, 0.5 moles of Cl₂ must react with (0.5 . 2) / 1 = 1 mol of K