corrected question: A chemist adds 135mL of a 0.21M zinc nitrate solution to a reaction flask. Calculate the mass in grams of zinc nitrate the chemist has added to the flask. Round your answer to significant digits.
Answer:
5.37g
Explanation:
0.21M means ; 0.21mol/dm³
1dm³=1L , so we can say 0.21mol/L
if 0.21mol of Zinc nitrate is contained in 1L of water
x will be contained in 135mL of water
x= 0.21*135*10³/1
=0.02835moles
number of moles= mass/ molar mass
mass= number of moles *molar mas
molar mass of Zn(NO₃)₂=189.36 g/mol
mass= 0.02835 *189.36
mass=5.37g
As the question tells you, you need to use the formula
% mass= mass of solute/ mass of solution x 100
mass solute= 30.0 g
mass of solution= 30.0 + 270.0= 300.0 g
% mass= 30.0/ 300.0 x 100= 10%
answer is B
It would be B.both solar thermal energy and solar electric energy.
<span>9.40x10^19 molecules.
The balanced equation for ammonia is:
N2 + 3H2 ==> 2NH3
So for every 3 moles of hydrogen gas, 2 moles of ammonia is produced. So let's calculate the molar mass of hydrogen and ammonia, starting with the respective atomic weights:
Atomic weight nitrogen = 14.0067
Atomic weight hydrogen = 1.00794
Molar mass H2 = 2 * 1.00794 = 2.01588 g/mol
Molar mass NH3 = 14.0067 + 3 * 1.00794 = 17.03052 g/mol
Moles H2 = 4.72 x 10^-4 g / 2.01588 g/mol = 2.34140921086573x10^-4 mol
Moles NH3 = 2.34140921086573x10^-4 mol * (2/3) = 1.56094x10^-4 mol
Now to convert from moles to molecules, just multiply by Avogadro's number:
1.56094x10^-4 * 6.0221409x10^23 = 9.400197448261x10^19
Rounding to 3 significant figures gives 9.40x10^19 molecules.</span>
Answer:
56160grams
Explanation:
First, we need to convert the number of molecules of magnesium chloride (MgCl2) into moles by dividing by Avagadro's number (6.02 × 10^23 molecules)
n = nA ÷ 6.02 × 10^23
n = 14.07 × 10^26 ÷ 6.02 × 10^23
n = 14.07/6.02 × 10^(26-23)
n = 2.34 × 10^3 moles of MgCl2
The balanced reaction given in the question is as follows:
Mg + 2HCl → MgCl2 + H2
If 1 mole of Mg produced 1 mole of MgCl2
Then, 2.34 × 10^3 moles of Mg will also produce 2.34 × 10^3 moles of MgCl2.
Using mole = mass ÷ molar mass (MM)
Molar mass of Mg = 24g/mol
mass = mole × MM
mass = 2.34 × 10^3 × 24
mass = 56.16 × 10^3
mass = 56160grams.
