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3 years ago

Which selection contains elements that are NOT all in the same group?

Chemistry

1 answer:

Volgvan3 years ago

4 0

Answer:

Iron, copper , calcium

Explanation:

Iron , copper and calcium are present in three different groups.

Iron is present in group eight.

Copper is present in group eleven.

Calcium is present in group two.

Sodium , potassium and rubidium are present in same group i.e. group one. These are alkali metals.

Fluorine, chlorine and bromine are present in group seventeen. These are halogens.

Argon, Krypton and xenon are present in same group i.e, group eighteen. All are these noble gases.

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Calculate the molarity of a solution obtained dissolving 10.0 g of cobalt(Ⅱ) bromide tetrahydrate in enough water to make 450 mL

Vladimir [108]

Answer:

The molarity of the CoBr2•4H2O solution is 7.64 × 10-2 M

Explanation:

Cobalt (II) bromide tetrahydrate

• Cobalt - A transition metal with Roman numeral (II) → charge: +2 → Co2+

• Bromide - anion from group 7A → -1 charge → symbol: Br-

• Tetrahydrate- tetra- means 4 and hydrate is H2O

The chemical formula of the compound is: CoBr2•4H2O

We then need to determine the number of moles of CoBr2•4H2O since this is the only information missing for us to find molarity. Notice that the volume of the solution is already given.

We’re given the mass of CoBr2•4H2O. We can use the molar mass of CoBr2•4H2O4 to find the moles.

•The molar mass of CoBr2•4H2O is:

CoBr2•4H2O

1 Co x 58.93 g/mol Co = 58.93 g/mol

2 Br x 79.90 g/mol Br = 159.80 g/mol

8 H x 1.008 g/mol H = 8.064 g/mol

4 O x 16.00 g/mol O = 64.00 g/mol

________________________________________

Sum = 290.79 g/ mo

The moles of CoBr2•4H2O is:

= 10.0 g CoBr2•4H2O x $\frac{ 1 mol CoBr_2 . 4H_2O}{290.79 g CoBr_2 . 4H_2O}$

= 0.0344 mol CoBr2•4H

We know that the volume of the solution is 450 mL.

We can now calculate for molarity:

Convert mL to L → 1 mL = 10-3 L

Formula:

Molarity (M)= Mole of solute / Liters of solution

= 0.0344 mol CoBr2•4H / 450 mL x 1 ml / 10^ -3 L

= 0.0764

= 7.64 × 10-2 mol/L

8 0

4 years ago

A passenger elevator travels from the first floor to the 60th floor, a distance of 210 m, in 35s. What is the elevator’s speed?

d1i1m1o1n [39]

Answer:6m per second

Explanation:

4 0

3 years ago

One of the characteristics of an acid-base reaction is that this type of reaction forms water true or false

Julli [10]

True! Acid-base reactions will always form water and a salt (not necessarily table salt, though!).

4 0

3 years ago

Both male and female rats have genotype Bb. Based on the Punnett square below and according to Mendel’s law of dominance, which

olga2289 [7]

The offspring will have white hair is the correct answer, as white hair is the recessive gene.

3 0

2 years ago

Students in physics class are asked to find the relationship between the length of a pendulum (string with a weight at the botto

Goshia [24]

Answer:

1) $Time \ for \ pendulum \ swing \ left \ and \ right = 2 \times \pi \times \sqrt{\dfrac{Length \ of \ the \ pendulum \ string}{g} }$

2) The dependent variable = The time it takes for one pendulum swing

3) The independent variable = The length of the pendulum string with weight at the bottom

Explanation:

The relationship between the length of the pendulum string and the time it takes for one pendulum swing is giving as follows;

$T = 2 \cdot \pi \cdot \sqrt{\dfrac{L}{g} }$

Where;

T = The period of oscillation = The time to complete one oscillation =Two swings of the pendulum

L = The length of the pendulum

g = The acceleration due to gravity

Therefore, the time it takes for one pendulum swing is directly proportional to the square root of the length of the pendulum

The dependent variable = The time it takes for one pendulum swing

Th independent variable = The length of the pendulum string with weight at the bottom.

5 0

4 years ago