Answer:
Explanation:
To convert from moles to grams, the molar mass is used (mass of 1 mole). The values are the same as the atomic masses on the Periodic Table, but the units are grams per mole (g/mol) instead of atomic mass units.
<h3>1. Molar Mass</h3>
We are given the compound sodium hydroxide (NaOH) and we need to look up the molar masses of the individual elements.
- Na: 22.9897693 g/mol
- O: 15.999 g/mol
- H: 1.008 g/mol
The formula for the compound has no subscripts, so there is 1 mole of each element in 1 mole of the substance. We can simply add the molar masses.
- NaOH: 22.9897693 + 15.999 + 1.008 = 39.9967693 g/mol
This means there are 39.9967693 grams of sodium hydroxide in 1 mole.
<h3>2. Convert Grams to Moles </h3>
Use the molar mass we found as a ratio.
Since we are converting 17.6 grams of NaOH to moles, we multiply by this value.
Flip the ratio so the units of grams of NaOH cancel.
<h3>3. Round </h3>
The original measurement of grams has 3 significant figures, so our answer must have the same. For the number we calculated, that is the thousandth place.
The 0 in the ten thousandths place (in bold above) tells us to leave the 0 in the thousandth place.
17.6 grams of sodium hydroxide are equal to <u>0.440 moles of sodium hydroxide.</u>
Answer:
V = 5 cm³
ρ = 4 g/cm³
Explanation:
Step 1: Calculate the volume (V)
We have a wooden cuboid of dimensions 5 cm × 1 cm × 1 cm. We can calculate its volume using the following expression.
V = 5 cm × 1 cm × 1 cm
V = 5 cm³
Step 2: Calculate the density (ρ)
The density is equal to the mass divided by the volume.
ρ = m / V
ρ = 20 g / 5 cm³
ρ = 4 g/cm³
Answer:
An electric force is exerted between any two charged objects. Objects with the same charge, both positive and both negative, will repel each other, and objects with opposite charges, one positive and one negative, will attract each other.
Explanation:
Answer:
The specific heat of the metal is 0,50 J/gºC
Explanation:
Assume that no heat is lost to the surroundings
(Q = m . C . ΔT)metal + (Q = m . C . ΔT)water = 0
Let's replace our values.
55g . C . (18,7ºC - 75ºC) + 100g . 4,184 J/g·°C . (18,7ºC - 15ºC) = 0
55g . C . -56,3 ºC + 418,4J/·°C . 3,7ºC = 0
-3096,5 gºC . C + 1548,08 J = 0
1548,08 J = 3096,5 gºC . C
1548,08 J / 3096,5 gºC = C = 0,50 J/gºC
Answer:
- <em><u>Mendeleev produced the first orderly arrangement of known elements.</u></em>
- <em><u>Mendeleev used patterns to predict undiscovered elements.</u></em>
Explanation:
- <u>Mendeleev produced the first orderly arrangement of known elements and used patterns to predict the undiscovered elements.</u>
Those two statments are true.
For the time being there were some 62 known elements. Before Medeleev some schemes to order part of the elements were proposed, but Medeleev showed the relationship between the atomic mass and the properties of the elements (supports second choice). This arrangement is known as the periodic table.
More importantly, Mendeleev predicted correctly the existance and properties of unknown elements, which is his major contribution: he left blanket spaces which where gradually filled when new elements where discovered (this supports the fourth choice).
The first modern chemistry book was written by Antoine Lavoisier (this discards first option).
Mendeleev ordered the elements by increasing mass number (this discards third choice), which was corrected later by the scientist Henry Moseley, who ordered the elements by increasing atomic number (number of protons).
Isotopes were not known by Mendeleev times, so this discards the last option.
