Non metals.
metalloids are substances that have both properties of metallic and non-metallic
Answer:
Explanation:
We are asked to convert an amount in grams to moles. To do this, we use the molar mass. This is the number of grams in one mole of a substance. It is the same value numerically as the atomic mass on the Periodic Table, however the units are grams per mole, not atomic mass units.
Look up the molar masses for the individual elements.
- Sodium (Na): 22.9897693 g/mol
- Oxygen (O): 15.999 g/mol
Look back at the formula: Na₂O. Notice there is a subscript of 2 after sodium. This means there are 2 atoms of sodium in every molecule, so we have to multiply sodium's molar mass by 2 before adding oxygen's.
- Na₂O: 2(22.9897693 g/mol)+ 15.999 g/mol = 61.9785386 g/mol
Set up a ratio using the molar mass.
Multiply by the given number of grams.
Flip the ratio so the grams of sodium oxide can cancel each other out.
The original measurement of grams given has 3 significant figures, so our answer must have the same. For the number we calculated, that is the hundredth place.
The 4 in the thousandth place tells us to leave the 8.
There are <u>2.48 moles of sodium oxide</u> in 154 grams, so choice A is correct.
Answer:
In order to determine the rate at which the sediment layers were deposited
Explanation:
Iridium is an important element that belongs to the Platinum group and they are dominantly present in the asteroids and comets. They are the key evidence that suggests the occurrence of an asteroidal impact or a mass extinction event that has taken place in the geological past.
The presence of Iridium mixed with the clay sediments in the boundary between the Cretaceous and Tertiary (K-T boundary) suggested the mass extinction event that wiped out numerous life forms from the earth.
The famous scientist Dr. Luis Walter Alvarez suggested measuring the concentration of Iridium in this K-T boundary in order to determine the rate at which these sediment layers were deposited. They were able to determine that these Iridium elements were present due to the asteroid impact on earth, that wiped out the dinosaurs from the earth. They also considered that this element can be produced from the eruptions of volcanoes.
When an atomic nucleus emits an alpha particle it decay into an atom with atomic number 2 less and mass number 4 less. Thus Thorium 230 decay as follows.
230 90Th -------> 226 88Th + 4 2 He
thorium is in the atomic number 90 thus it during alpha decay it reduces to atomic number 88 while its 230 mass number reduces to 226
Molality= moles NaCl/ Kg H2O
250 g (1 Kg/ 1000 grams)= 0.250 Kg
Molality= 0.611 moles/ 0.250 Kg= 2.44 molal
