<u>Given:</u>
Mass of pure iron (Fe) = 3.4 g
<u>To determine:</u>
Mass of HBr needed to dissolve the above iron
<u>Explanation:</u>
Reaction between HBr and Fe is
Fe + 2HBr → FeBr₂ + H₂
Based on the reaction stoichiometry-
1 mole of Fe reacts with 2 moles of HBr
# moles of Fe = mass of Fe/atomic mass of Fe = 3.4/56 g.mol⁻¹ = 0.0607 moles
Therefore # moles of HBr = 2*0.0607 = 0.1214 moles
Molar mass of HBr = 81 g/mole
Mass of HBr = 0.1214 moles * 81 g/mole = 9.83 g
Ans: Mass of HBR required is 9.83 g
V1/T1 = V2/T2
Substitute the value use ratio and proportion. Use calculator.
V1 = (V2 x T1) / T2
1 is initial, 2 is final
16.4 grams is the mass of solute in a 500 mL solution of 0.200 M
.
sodium phosphate
Explanation:
Given data about sodium phosphate
atomic mass of Na3PO4 = 164 grams/mole
volume of the solution = 500 ml or 0.5 litres
molarity of sodium phosphate solution = 0.200 M
The formula for molarity will be used here to know the mass dissolved in the given volume of the solution:
The formula is
molarity = 
putting the values in the equation, we get
molarity x volume = number of moles
0.200 X 0.5= number of moles
number of moles = 0.1 moles
Atomic mass x number of moles = mass
putting the values in the above equation
164 x 0.1 = 16.4 grams
16.4 grams of sodium phosphate is present in 0.5 L of the solution to make a 0.2 M solution.
Answer:
True
Explanation:
magnesium and copper react with dilute acids to make salts and hydrogen gas
Answer: The correct answer is the option: B. An element with eight valence electrons is chemically unstable.
Explanation:
Hello! Let's solve this!
We will analyze each of the options:
A. The group number of the element provides a clue to the number of valence electrons: it is correct, since it provides the number of valence electrons.
B. An element with eight valence electrons is chemically unstable: this is not correct, since elements with eight electrons in the valence shell cannot react because they already have the last complete shell. Therefore, they are chemically stable.
C. The points must be placed one at a time on each side of the chemical symbol: it is correct, because that is the way to make the point diagram.
D. An atom is chemically stable if all the points are paired: this is correct since this verifies that the point diagram has been done well.
We conclude that the correct answer is the option: B. An element with eight valence electrons is chemically unstable.
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