Answer:
36.66%
Explanation:
Step 1: Given data
- Mass of the sample: 2.875 g
Step 2: Calculate the mass of salt
The mass of the sample is equal to the sum of the masses of the components.
m(sample) = m(iron) + m(sand) + m(salt)
m(salt) = m(sample) - m(iron) - m(sand)
m(salt) = 2.875 g - 0.660 g - 1.161 g
m(salt) = 1.054 g
Step 3: Calculate the percent of salt in the sample
We will use the following expression.
%(salt) = m(salt) / m(sample) × 100%
%(salt) = 1.054 g / 2.875 g × 100% = 36.66%
<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>
Answer:
6. O₂ + Cu —> CuO
7. H₂ + Fe₂O₃ —> H₂O + Fe
8. O₂ + H₂ — > H₂O
9. H₂S + NaOH —> Na₂S + H₂O
10. Al + HCl —> H₂ + AlCl₃
Explanation:
6. Oxygen gas react with solid copper metal to form copper(II) oxide
Oxygen gas => O₂
Copper => Cu
copper(II) oxide => CuO
The equation is:
O₂ + Cu —> CuO
7. hydrogen gas and iron(III) oxide powder react to form liquid water and solid iron power
hydrogen gas => H₂
Iron(III) oxide => Fe₂O₃
Water => H₂O
Iron => Fe
The equation is:
H₂ + Fe₂O₃ —> H₂O + Fe
8. Oxygen gas react with hydrogen gas to form liquid water
Oxygen gas => O₂
hydrogen gas => H₂
Water => H₂O
The equation is:
O₂ + H₂ — > H₂O
9. Hydrogen sulphide gas is bubbled through a sodium hydroxide solution to produce sodium sulphide and liquid water
hydrogen sulphide => H₂S
sodium hydroxide => NaOH
Sodium sulphide => Na₂S
Water => H₂O
The equation is:
H₂S + NaOH —> Na₂S + H₂O
10. Hydrogen gas and aluminum chloride solutions are produced when solid aluminum react with hydrochloric acid
Aluminum => Al
Hydrochloric acid => HCl
hydrogen gas => H₂
Aluminum chloride => AlCl₃
The equation is:
Al + HCl —> H₂ + AlCl₃
Answer:
THE EMPIRICAL FORMULA OF THE SUBSTANCE IS C2H5NO
Explanation:
The steps involved in calculating the empirical formula of this substance in shown in the table below:
Element Carbon Hydrogen Nitrogen Oxygen
1. % Composition 40.66 8.53 23.72 27.09
2. Mole ratio =
%mass/ atomic mass 40.66/12 8.53/1 23.72/14 27.09/16
= 3.3883 8.53 1,6943 1.6931
3. Divide by smallest
value (0.6931) 3.3883/1.6931 8.53/1.6931 1.6943/1.6931 1.6931/1.6931
= 2.001 5.038 1.0007 1
4. Whole number ratio 2 5 1 1
The empirical formula = C2H5NO
Answer : The incorrect option is, The most of the mass of the atom comes from the electron cloud.
Explanation :
There are three basic particles of an atom which are neutrons, protons and electrons.
The nucleus which is present in the center of an atom that contains the neutrons and the protons. The protons are positively charged and neutrons has no charge.
The outer region of an atom contains the electrons and the electrons are negatively charged.
As per given options, the statement which is the most of the mass of the atom comes from the electron cloud is incorrect statement because the most of the mass comes from the nucleus in which protons and neutrons are present.