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3 years ago

Why do scientist record observations during an experiment?

1 answer:

3 0

Observation is more than simply noticing something. ... Observation is essential in science. Scientists use observation to collect and record data, which enables them to construct and then test hypotheses and theories.

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A laboratory technician combined sodium hydroxide with excess iron(II) nitrate. A reaction took place according to this chemical

Whitepunk [10]

The initial mass of sodium hydroxide is 3.3 g (answer C)

<u><em>calculation</em></u>

Step 1 : find the moles of iron (ii) hydroxide ( Fe(OH)₂

moles = mass÷ molar mass

from periodic table the molar mass of Fe(OH)₂ = 56 + [16 +1]2 = 90 g/mol

moles is therefore = 3.70 g÷ 90 g/mol = 0.041 moles

Step 2: use the mole ratio to calculate the moles of sodium hydroxide (NaOH)

from given equation NaOH : Fe(OH)₂ is 2 :1

therefore the moles of NaOH = 0.041 x 2 = 0.082 moles

Step 3: find mass of NaOH

mass = moles x molar mass

from the periodic table the molar mass of NaOH = 23 +16 +1 = 40 g/mol

mass = 0.082 moles x 40 g/mol = 3.3 g ( answer C)

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3 years ago

Which of the following increases as you move up a column of the periodic table?

luda_lava [24]

Answer:

electronegativity increases

6 0

3 years ago

A student knows that hydrogen (H) atoms and oxygen (O) atoms combine to form water (H2O). The student correctly predicts that hy

marusya05 [52]

Answer:

Explanation:

They both need to lose 2 electrons to form ions

6 0

3 years ago

A chemical reaction produces 3.81g potassium chloride (KCl). How many formula units of potassium chloride are there? *Find Molar

Aleks04 [339]

Answer:

The number of formula units in 3.81 g of potassium chloride (KCl) is approximately 3.08 × 10²²

Explanation:

The given parameters is as follows;

The mass of potassium chloride produced in the chemical reaction (KCl) = 3.81 g

The required information = The number of formula units of potassium chloride (KCl)

The Molar Mass of KCl = 74.5513 g/mol

$The \ number \ of \ moles \ of \ a \ substance, n = \dfrac{The \ mass \ of \ the substance}{The \ Molar \ Mass \ of \ the \ substance}$

Therefore, we have;

$The \ number \ of \ moles \ of \ KCl= \dfrac{3.81 \ g}{74.5513 \ g/mol} \approx 0.051106 \ moles$

1 mole of a substance, contains Avogadro's number (6.022 × 10²³) of formula units

Therefore;

0.051106 moles of KCl contains 0.051106 × 6.022 × 10²³ ≈ 3.077588 × 10²² formula units

From which we have, the number of formula units in 3.81 g of potassium chloride (KCl) ≈ 3.08 × 10²² formula units.

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3 years ago

3 A soil has 70% sand, 20% silt

Kisachek [45]

Today, as part of the series of posts on soils, we are going to look at ‘soil texture’. Soil forms the basis for all life but it’s important to know about its mineral constitution as well as its biological profile.

Texture refers to the ‘feel’ of the soil. This is affected by the constituent materials found within it, specifically sand, silt and clay particles. A coarse sand will feel gritty but a wet clay will feel heavy and sticky. The texture of a soil has a direct impact on the way the soil reacts to certain environmental conditions – for example, towards drought or heavy rain (with sandy soils more freely draining).

There is a big difference in the size of the different particles.

Coarse sand = diameter 2-0.2mm

Fine sand = diameter 0.2-0.02mm

Silt = diameter 0.02-0.002mm

Clay = diameter less than 0.002mm

Note how the clay particles are much smaller than the sand particles – this is important as it means the total surface area of a clay soil is much greater and so the capacity to hold water is also much greater.

Between the sand, silt and clay particles there are lots of pores. In fact a soil as a whole is generally 45% mineral, 5% organic matter (depending on the soil) and 50% pore space through which air and water can pass.

Sand –

Made up of weathered primary rock minerals.

The particles are irregular in outline.

They are large and so do not pack together easily.

Large pore spaces in between.

Air gets in very easily and water flows rapidly through it.

Silt –

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3 years ago