<span>A chemist adds 155.0ml of a 4.10 X 10^-5 mmol/L of a zinc oxalate (ZnC2O4)solution to a reaction flask. Calculate the mass in micrograms of zinc oxalate the chemist has added to the flask.
1mmol = 10^-3 mol
Therefore 4.10*10^-5mmol = 4.10*10^-8mol
molar mass ZnC2O4 = 65.39+(2*12.011)+(4*15.99) = 153.372g/mol
You have 4.10*10^-8 mol/litre =153.372 * 4.10*10^-8 = 6.29*10^-6 grams / litre (* see below)
But you have 155ml. Mass of ZnC2O4 = 155/1000*6.29*10^-6 g
Mass is = 9.75*10^-7 grams
1µg = 10^-6 g
You then have 9.75*10^-7/10^-6 = 0.975µg ZnC2O4
(*see below) at this point you could have said:
1µg = 10^-6 g therefore you have a solution of 6.29µg per litre,
155ml = 6.29*155/1000 = 0.975µg ZnC2O4</span>
4. A
because PbCl2 is an ionic compound and it's solid, so it's a substance.
It cannot be mixture, because it's a pure molecule.
5. D
despite that both substances are gases, colorless they are different molecules, so they should have different either chemical and physical properties
6. C
this substance made from W atoms and others are made from molecules
The quality or state of being volcanic.
Answer:
151.4863 years
Explanation:
Half life, t1/2 = 100 years
Initial concentration,[A]o = 100%
Final concentration, [A] = 35% (after 65% have been decayed)
Time = ?
Half life for a first Order reaction is given as;
t1/2 = ln (2) / k
k = ln(2) / 100
k = 0.00693y-1
The integral rate law for first order reactions is given as;
ln[A] = ln[A]o − kt
kt = ln[A]o - ln[A]
t = ( ln[A]o - ln[A]) / k
t = [ln(100) - ln(35)] /0.00693
t = 1.0498 / 0.00693
t = 151.4863 years
Answer:
2 HC₂H₃O₂(aq) + Sr(OH)₂(aq) ⇒ Sr(C₂H₃O₂)₂(aq) + 2 H₂O
Explanation:
Let's consider the reaction between acetic acid and strontium hydroxide. This is a neutralization reaction, in which an acid reacts with a base to form salt and water. The unbalanced equation is:
HC₂H₃O₂(aq) + Sr(OH)₂(aq) ⇒ Sr(C₂H₃O₂)₂(aq) + H₂O
We have 1 acetate ion to the left and 2 to the right, so we will multiply HC₂H₃O₂(aq) by 2.
2 HC₂H₃O₂(aq) + Sr(OH)₂(aq) ⇒ Sr(C₂H₃O₂)₂(aq) + H₂O
Finally, we multiply water by 2 to get the balanced equation.
2 HC₂H₃O₂(aq) + Sr(OH)₂(aq) ⇒ Sr(C₂H₃O₂)₂(aq) + 2 H₂O
