Weight percentage of nitrogen can be calculated using the following rule:
weight percentage of nitrogen = (weight of nitrogen / weight of urea) x 100
From the periodic table:
molecular mass of carbon = 12 grams
molecular mass of nitrogen = 14 grams
molecular mass of hydrogen = 1 grams
molecular mass of oxygen = 16 grams
therefore:
mass of nitrogen in urea = 2(14) = 28 grams
mass of urea = 12 + 2(14) + 4(1) + 16 = 60 grams
Substitute with the masses in the equation to get the percentage:
weight percentage of nitrogen = (28/60) x 100 = 46.667%
Answer:
D) burning a candle
A demonstration that contains both physical and chemical changes will be BURNING OF A CANDLE.
<em>This is because when a candle is lighted up, on the top of it (where we see flame) the oxygen and other gases present around will be chemically changed (burned up)</em>
<em>When the wax in the top of the candle will get melted due to the heat of the fire a physical change takes places.</em>
Answer:
- Britta paid more per kilometer driven
Explanation:
<u>1) Britta:</u>
- Distance traveled: 1,250 Km
- Gasoline price: 1.23 euros / liter
Cost per km = total cost of gasoline / distance traveled
Cost per km = gasoline used × gasoline price / distance traveled
Cost per km = 209 liter × 1.14 (euro / liter) / 1,250 km = 0.19 euro / km
<u>2) Pierce:</u>
- Distance traveled: 1,405 km
- Gasoline price = 1.23 euros / liter
Cost per km = 175 liter × 1.23 (euro / liter) / 1,405 km = 0.15 euro / km
<u>3) Comparison:</u>
- 0.19 > 0.15 ⇒ Britta paid more per kilometer driven
Rutherford theorized that atoms have their charge concentrated in a very small nucleus.
This was famous Rutherford's Gold Foil Experiment: he bombarded thin foil of gold with positive alpha particles (helium atom particles, consist of two protons and two neutrons).
Rutherford observed the deflection of alpha particles on the photographic film and notice that most of alpha particles passed straight through foil.
That is different from Plum Pudding model, because it shows that most of the atom is empty space.
According to Rutherford model of the atom:
1) Atoms have their charge concentrated in a very small nucleus.
2) Major space in an atom is empty.
3) Atoms nucleus is surrounded by negatively charged particles called electrons.
4) An atom is electrically neutral.
Answers and explanation:
To answer these questions you use a periodic table.
A is In because it has 49 protons and In is element number 49.
B is 27 because Co is element number 27.
C is 73 because Ta is element number 73.
D is 49 because the number of electrons in an atoms is always equal to the number of protons.
E is 56 because the atomic number of Ba is 56.
F is 54 because 56 - 54 = 2. The charge is equal to the number of protons minus the number of electrons.
G is 66. The number of neutrons is equal to the atomic mass minus the number of protons. 115 - 49 = 66.
H is 108 because 181 - 73 = 108.
I is 32. The atomic mass of an element is equal to the amount of protons plus the amount of neutrons. So 16 + 16 = 32.
