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3 years ago

Calcium hydroxide and hydrogen gas are produced by the reaction of calcium hydride and water

Chemistry

2 answers:

Sever21 [200]3 years ago

7 0

Answer: B) calcium hydride + water -> calcium hydroxide + hydrogen

Explanation: B) on EDG

DanielleElmas [232]3 years ago

3 0

Explanation:

The reaction forms calcium hydroxide, Ca(OH)2 and hydrogen gas (H2). The calcium metal sinks in water and after an hour or so bubbles of hydrogen are evident, stuck to the surface of the metal.

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Thirty grams of potassium chloride crystals are added to 400 mL of water. What is the molarity of this potassium chloride soluti

photoshop1234 [79]

Answer:

Molarity of potassium chloride is:

A. 1.0 M

Explanation:

Molarity is used to express the concentration of the solution.It is defined as the moles of solutes per liter volume of solution.It is denoted by M.

$molarity(M)=\frac{moles\ of\ solute}{volume\ of\ solution(ml)}\times 1000$

$M=\frac{n}{V(ml)}\times 1000$

Here'n' is the number of moles. It can be calculated using formula:

$n=\frac{given\ mass(w)}{molar\ mass}$

given mass=30 gm

Molar mass of KCl = mass of K+mass of Cl

= 39.098+34.45

= 74.55 g

$n=\frac{30}{74.55}$

n = 0.402 moles

$M=\frac{n}{V(ml)}\times 1000$

$M=\frac{0.402}{400}\times 1000$

$M=\0.001\times 1000$

M=1.00 M

So molarity of potassium chloride is 1.00 M

5 0

4 years ago

Three samples of a solid substance composed of elements A and Z were prepared. The first contained 4.31 g A and 7.70 g Z. The se

murzikaleks [220]

Answer:

The percentage composition of the elements of the compound in the three samples is the same.

Explanation:

<em>The law of definite proportions states that all pure samples of a particular chemical compound contain the same elements in the same proportion by mass.</em>

Sample A:

Mass of A = 4.31 g; mass of Z = 7.70 g

Total mass of sample = 12.01

Percentage mass of A in the sample = (4.31 * 100)/12.01 = 35.9 %

Percentage mass of Z in the sample = (7.70 * 100)/12.01 = 64.1 %

Sample B:

Percentage mass of A in the sample = 35.9 %

Percentage mass of Z in the sample = 64.1 %

Sample C:

Mass of A = 0.718 g; Total mass of sample = 2.00 g

mass of Z = mass of sample - mass of A = 2.00 g - 0.718 g = 1.282 g

Percentage mass of A in the sample = (0.718 * 100)/2.00 = 35.9 %

Percentage mass of Z in the sample = (1.282 * 100)/2.00 = 64.1 %

From the calculations, it can be seen that the percentage composition of the elements in the compound is the same for the three samples.

8 0

4 years ago

PLEASE HELP ASAP !!!!!!!!!!!!!!!!!!!!!!!!!!!!!

In-s [12.5K]

+2, because the element has more protons than electrons now

5 0

4 years ago

Specify the l and ml values for n = 4.

Bumek [7]

Answer : The specify the l and ml values for n = 4 are:

At l = 0, $m_l=0$

At l = 1, $m_l=+1,0,-1$

At l = 2, $m_l=+2,+1,0,-1,-2$

At l = 3, $m_l=+3,+2,+1,0,-1,-2,-3$

Explanation:

There are 4 quantum numbers :

Principle Quantum Numbers : It describes the size of the orbital. It is represented by n. n = 1,2,3,4....

Azimuthal Quantum Number : It describes the shape of the orbital. It is represented as 'l'. The value of l ranges from 0 to (n-1). For l = 0,1,2,3... the orbitals are s, p, d, f...

Magnetic Quantum Number : It describes the orientation of the orbitals. It is represented as m_l. The value of this quantum number ranges from $(-l\text{ to }+l)$ . When l = 2, the value of $m_l$ will be -2, -1, 0, +1, +2.

Spin Quantum number : It describes the direction of electron spin. This is represented as $m_s$ The value of this is $+\frac{1}{2}$ for upward spin and $-\frac{1}{2}$ for downward spin.